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2018 | Book

# High Performance Structural Materials

## Proceedings of Chinese Materials Conference 2017

Editor: Prof. Yafang Han

Publisher: Springer Singapore

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This proceedings volume gathers selected papers presented at the Chinese Materials Conference 2017 (CMC2017), held in Yinchuan City, Ningxia, China, on July 06-12, 2017.

This book covers a wide range of powder metallurgy, high performance aluminum alloys, high performance titanium & titanium alloys, superalloys, metal matrix composite, space materials science and technology, rare metals, refractory metals and their applications, advanced ceramics materials, nanostructured metals and alloys.

The Chinese Materials Conference (CMC) is the most important serial conference of the Chinese Materials Research Society (C-MRS) and has been held each year since the early 1990s. The 2017 installment included 37 Symposia covering four fields: Advances in energy and environmental materials; High performance structural materials; Fundamental research on materials; and Advanced functional materials. More than 5500 participants attended the congress, and the organizers received more than 700 technical papers. Based on the recommendations of symposium organizers and after peer reviewing, 490 papers have been included in the present proceedings, which showcase the latest original research results in the field of materials, achieved by more than 300 research groups at various universities and research institutes.

##### Effects of Internal Oxidation Methods on Microstructures and Properties of Al2O3 Dispersion-Strengthened Copper Alloys

With Cu–Al alloy powder as raw material and Cu2O powder as oxidant, two internal oxidation methods, namely step-by-step internal oxidation-reduction method (referred to as the step-by-step method) and integrated internal oxidation-reduction method (referred to as the integrated method), were respectively adopted to achieve the oxidation of Al. Then hot extrusion without canning was applied to prepare Al2O3 dispersion-strengthened copper alloys. The effects of the two internal oxidation methods on microstructures and properties of the alloys were compared. The results show that both the step-by-step method and the integrated method can achieve the complete oxidation of Al. However, the excessive oxidant can not be reduced thoroughly in the integrated method. The residual oxidant increases oxidation of the sintered body during hot extrusion and the formed copper oxides distribute in the grains as well as at the grain boundaries. While in the step-by-step alloy, the copper oxides mainly distribute at the grain boundaries. The step-by-step method improves electrical conductivity and ductility, but lowers hardness and strength. The integrated alloy has worse ductility and lower electrical conductivity, but strength and hardness are higher. The step-by-step alloy has better comprehensive properties, and its electrical conductivity, hardness, tensile strength, yield strength and elongation is 89% IACS, HRB 69–72, 425 MPa, 394 MPa and 27.2%, respectively.

Feng Chen, Zhiqiao Yan, Tao Wang
##### Effects of Al Content on the Physical Properties of Al2O3 Dispersion-Strengthened Copper Alloys

Based on three kinds of CuAl alloy powders with Al mass fraction of 0.18, 0.55 and 1.95%, respectively, as raw materials and Cu2O powder as oxidant, three dispersion-strengthened copper alloy powders with Al2O3 content of 0.34, 1.00 and 3.19%, respectively, were prepared by internal oxidation using the optimal internal oxidation parameter. Hot pressing was subsequently adopted to prepare Al2O3 dispersion-strengthened copper (Cu–Al2O3) alloys. The effects of Al2O3 content on microstructures and properties of alloy powders and sintered alloys were studied. The results showed that the microhardness of three alloy powders after internal oxidation was significantly improved and increased with increasing Al2O3 content. But the difference between powders with 1.00 and 3.19% Al2O3 content was small. The relative densities of sintered alloys with lower Al2O3 content, i.e. 0.34 and 1.00%, were both above 99%. However that with higher Al2O3 content, i.e. 3.19%, was only 97.8%. With increasing Al2O3 content, electrical conductivity decreased and hardness increased obviously. The electrical conductivity and hardness (HRB) of three alloys were 86.0, 71.5, 60.0% IACS, and 68.8, 84.3, 91.0, respectively.

Zhiqiao Yan, Feng Chen, Tao Wang
##### Synthesis of Beryllium Pebbles Using Plasma Rotating Electrode Process

Beryllium is used as neutron multiplier in the form of a pebble bed. Basic characteristics of the beryllium pebbles are required to the design of blanket. From this point view, production methods and basic characteristics including particle morphology and mechanical properties of beryllium pebbles were investigated. The paper gives a brief description of fabrication technology for the Be pebbles. The Plasma Rotating Electrode Process (PREP) is the method for producing 1–1.2 mm Be pebbles for use as a neutron multiplier. The obtained results indicate the advantages for the fabrication of Be pebbles and the excellent properties of the pebbles.

Yumei Jia, Yongjin Feng, Jianli Zhang, Pingping Liu, Qian Zhan, Farong Wan
##### Preparation and Characterization of Fine 316L Stainless Steel Powders Prepared by Gas Atomization

Atomization technique has the powder production advantages of high production efficiency, low cost and good sphericity. In this paper, 316L stainless steel powders were prepared in nitrogen atmosphere by using self-designed nozzles. The fine powders yield, particle size distribution, particle shape and microstructure of powders prepared by different nozzles and different pressure were studied. Particle analyzer was used to characterize the powders. Results show that the powders produced by more complex nozzle structures and higher pressure have higher yield and better effect sphericity. The slender powders are fewer. The average elongation is below 0.4, and the average O.Bluntness values are above 0.6. With the decrease of pressure, the average of O.Bluntness value increases and the sphericity of powders is improved. The average outgrowth values are below 0.2, and the satellite powders are lesser when the pressure is greater. The flowability of the 316L stainless steel powders prepared by lower pressure were better, while the powders prepared by the higher pressure have extremely poor fluidity. The fluidity was significantly improved after sieving the fine powders less than 25 µm. The surface and the internal microstructure of 316L stainless steel powders prepared by different processes are mainly cellular and dendrite structures.

Yingying Chen, Zhiyu Xiao, Haiping Zou, Shangkui Li, Aihong Li
##### Microstructure and Mechanical Properties of 1.2709 Die Steel by Selective Laser Melting

The differences of microstructure and mechanical properties of die steel (1.2709) prepared by selection of laser melting (SLM) process and traditional casting-forging process were studied. Sample A was prepared by SLM process. Sample B was prepared by mixing process (half volume using conventional casting—half volume of forging process application SLM). Sample C was prepared by traditional casting–forging process. Three sets of samples were subjected to the same process of solution treatment and aging treatment. The microstructures and mechanical properties of the three groups were studied. The results showed that the microstructure of sample A was a homogeneous and dense plate-like martensite structure, and they were different in phase distribution. The microstructure observation of sample B indicated that the part of the conventional casting-forging process consisted of martensite and carbide particles, but the SLM process consisted of a uniformly distributed elongated martensite structure. In the region of different forming process, there was a transition region with a width of 40 μm. The transition zone was relatively loose and the defects were relatively more. The microstructure of conventional casting–forging process 1.2709 die steel samples was mainly composed of lath martensite and carbide particles. In addition, the relative densities of the three sets of samples were close to 100%. The impact toughness values αKV, αKU and the impact absorbing energy KV2, KU2 of sample B, sample A and sample C showed an increasing trend, and the mechanical property difference was less than 15%. It is proved that the mechanical properties of 1.2709 die steel workpiece prepared by SLM process can meet the needs of engineering application.

Mingyue Zheng, Shaoming Zhang, Jun Xu, Jinhui Zhang, Qiang Hu, Huijun He, Xinming Zhao
##### A Comparative Corrosion Study on Traditional and Melt-Spinning 7075 Al Alloy

Rapidly solidified 7075 Al alloy ribbons were prepared by melt-spinning. Sintered 7075 compacts with fine-grain microstructure were obtained by spark plasma sintering of the chopped melt-spun ribbons at different sintering temperatures. The corrosion behavior of the sintered 7075 alloy was examined and compared to that of the 7075-T6 bulk by electrochemical and immersion experiments carried out in NaCl solution. Microstructures of the consolidated samples before and after corrosion tests were examined by optical microscope and scanning electron microscope. Ratios of corrosion after immersion tests were measured by an image analyzing software. Results of this study suggest that the sintered material exhibited slightly poorer corrosion resistance than the bulk 7075 alloy and the porosity adversely affect the corrosion behaviors of the sintered material.

Sieglind Ngai, Tungwai Ngai, Yongliang Ou, Weipeng Zhang, Liejun Li
##### Preparation of Fe/Fe3O4 Soft Magnetic Composites by Spark Plasma Sintering

Fe/Fe3O4 soft magnetic composite was prepared with the method of physical coating method by spark plasma sintering. In this way, its sintering interface was improved. It solved the problem that hot pressing curing soft magnetic composites have low densification. The Fe/Fe3O4 was observed at different sintering temperatures and the influence of the chemical composition and microstructure properties was analyzed. The material density was higher and interface was combined with high performance. The resistivity decreases because the element changed with higher temperature. The morphology and structure are characterized by SEM, EDS and XRD, respectively and the electric properties are tested. In the end part we discuss the pros and cons of SPS method on synthesizing Fe/Fe3O4 soft magnetic composites and its potential application in industries.

Shuhan Lu, Jihang Ren, Zhankui Zhao
##### High-Quality Ti–6Al–4V Alloy Powder Prepared by Plasma Rotating Electrode Process and Its Processibility in Hot Isostatic Pressing

High quality Ti–6Al–4V alloy powders were prepared by plasma rotating electrode process (PREP). Three different rotating speed were selected. After sieved, three kinds of powder with different size distribution were consolidated by hot isostatic pressing (HIP). The phase compositions, morphologies and microstructures of the powders and HIPed samples were characterized. Mechanical properties of HIPed Ti–6Al–4V alloys also were investigated. The results showed that the proportion of small particles increased with the increasing rotating speed. Alloy prepared by powders distributed in 100–150 μm possesses the best mechanical properties.

Liming Zou, Xin Liu, Huanwen Xie, Xinhua Mao
##### Microstructure and Mechanical Properties of Hot-Rolled 5E83 Alloy

Hot-rolling plates of Al–4.5Mg–0.7Mn–0.2Zr–0.2Er alloy were prepared under the reduction of 50%, and tensile property, impact toughness were measured at the temperatures varying from 200–470 °C. The microstructure of the hot-rolling plates was investigated using scanning electron microscopy and transmission electron microscopy. The results showed that the tensile strength and yield strength decreased with the rise of the hot-rolling temperature, the elongation and impact toughness showed the opposite trend, and the best match between strength and toughness was at the rolling temperature of 350 °C. The second phase particles in the alloy had a great influence on the impact toughness and plasticity of the alloy. As the rolling temperature increased, the dynamic recovery and dynamic recrystallization occurred in the alloy. Dispersed Al3(Er, Zr) particles formed in the alloy when Er and Zr were added. The Al3(Er, Zr) particles were able to pin dislocation motion, hinder the growth of subgrains and the migration of grain boundaries, thereby inhibited the dynamic recrystallization of Al–4.5Mg–0.7Mn–0.2Zr–0.2Er alloy and its thermal stability improved.

Xin Li, Wei Wang, Hui Huang, Xiaoli Liu, Yifei Liu, Hongbo Wang, Shengping Wen, Xiaolan Wu, Kunyuan Gao, Zuoren Nie
##### Microstructure and Properties of Spray-Formed Si–30Al Alloy Used for Electronic Packaging

The microstructure and properties of spray-formed Si–30Al alloy was studied in this paper, which was used for electronic packaging. Hot isostatic pressing was used to compact the ingot, and then electroplating and brazing was carried out. The results showed that, (1) the Si–30Al alloy comprised α-Al phase, pseudo eutectic phase and primary silicon phase; (2) the flow deformation of α-Al phase and pseudo eutectic phase filled pore defect making the alloy compacting by HIP; (3) the alloy could be electroplated and brazed easily, and no pore defect was observed in electroplated coating and weld.

Hongwei Liu, Shuhui Huang, Zhihui Li, Baiqing Xiong, Yongan Zhang, Xiwu Li, Hongwei Yan, Lizhen Yan
##### Effect of Erbium–Zirconium Composite Modifications on the Microstructure and Mechanical Properties of A356 Aluminum Alloy

The Al–7Si–0.3 Mg (A356) alloys with various contents of the rare earth element Er, Zr were prepared by the conventional casting technique. The effect of Er, Zr composite modifications on the microstructure and mechanical properties of A356 alloys was investigated using the optical microscopy (OM), scanning electronic microscopy (SEM), energy spectrum analysis and mechanical testing. The results show that addition of 0.3 wt% Er and Zr had an excellent refining effect on α-Al grains and a modification effect on Si containing phase in the as-cast state. The size of α-Al dendrite reduced, the acicular eutectic Si became short rod-shaped or granular. When Er and Zr content was 0.3 wt%, the tensile strength and hardness of the alloys reached up to maximum values.

Liantao Ji, Wei Wang, Hui Huang, Shengping Wen, Kunyuan Gao, Xiaolan Wu
##### Modeling and Simulation of Dynamic Recrystallization Behaviors of 7085 Aluminum Alloy During Hot Deformation Using Cellular Automata Method

Cellular Automata (CA) method can be used to simulate the microstructure evolution. The parameters of the CA model and thermal deformation parameters are input to the CA model as important data. The hot deformation behavior was studied by means of a hot simulating test on Geleeble-1500 experiment machine. The range of thermal deformation temperature is 623–723 K, the range of strain rate is 0.001–1 s−1 and the maximum true strain is 0.91. Analysis of microstructure of average grain size and recrystallization fraction by optical microscope (OM) and electron backscatter diffraction (EBSD). CA model was used to study the effects of strain, strain rate and deformation temperature on the deformed microstructure. The simulation results are validated by a great deal of experimental data, the simulation results are in good agreement with the experimental data that shows the feasibility and predictability of the CA method.

Jie Zhang, Zhihui Li, Shuhui Huang, Xiwu Li, Lizhen Yan, Hongwei Yan, Hongwei Liu, Yongan Zhang, Baiqing Xiong
##### Aging Time on the Microstructure and Mechanical Properties of A356 Alloy by Semi-solid Processing

An investigation was carried out to study the effects of aging time on the microstructure and mechanical properties of A356 alloy by semi-solid processing. The alloy was subjected to solution treatment for 4 h at 540 °C, artificial ageing was carried out at temperature (170 °C) and different time (0–24 h). The results revealed that the needle-shaped eutectic Si phase in as-cast ingot was transformed to globular shape compared with that by solution treatment. Meanwhile the Chinese script π-Fe(AlMgSiFe) phase was transformed to smaller and uniformly distributed β-Fe(AlFeSi) phase, the elongation increased obviously. With the increasing of aging time, the elongation decreased, and the ultimate tensile strength increased. When the aging time was 4 h, the alloy achieved the optimal mechanical properties. The micro-hardness was 121HV, ultimate tensile strength was 329 MPa, and the elongation was 15%. From the fracture morphology, the fracture for alloy aging for 4 h showed more dimples. With the increasing of aging time, the ultimate tensile strength and the elongation decreased.

Peng Qi, Bolong Li, Wenjian Lv, Shasha Dong, Tongbo Wang, Ning Li, Zuoren Nie
##### Homogenization Treatment and Kinetic Analysis of 2297 Al–Li Alloy

The microstructure evolution and composition distribution of the industrially cast 2297 Al–Li alloy during single-stage and double-stage homogenization were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and differential scanning calorimetry (DSC). The results show that severe dendrite segregation exists in the as-cast alloy. Cu, Fe and Mn elements have obvious segregation at grain boundaries, and the degree of enrichment decreases gradually from grain boundary to intracrystal. The undissolved phases in the grain boundaries are mainly Al2Cu phase and Fe and Mn containing phase. The optimal single-stage homogenization treatment system is 525 °C × 24 h. And the optimal double-stage homogenization system is 460 °C × 20 h + 525 °C × 24 h. After double-stage homogenization treatment, non-equilibrium eutectic phase on the grain boundary fully dissolved, and the segregation of dendrite is eliminated. At the same time, the size of Al3Zr particles is uniform and distributed dispersion, while no dissolved Fe and Mn containing phase is found at grain boundaries. The mechanism of the double-stage homogenization treatment agrees with the results of kinetic analysis.

ShengLi Yang, Jian Shen, Peng Jiang, PeiYue Li, Yan Yu, DeJun Song, Huan Tao, Wei Guo, Wen Fu
##### The Microstructure Evolution of Al–Mg–Si–Mn–Er–Zr Alloy During Homogenization

The formation of non-equilibrium intermetallic phases during solidification significantly deteriorates the mechanical properties of Al–Mg–Si–Mn–Zr–Er alloy, but homogenization heat treatment can effectively reduce these residual phases. Therefore, it is necessary to study the evolution of these non-equilibrium intermetallic phases during different homogenization treatment. In this study, the methods we used are OM, SEM in combination with EDS, XRD and TEM. The results showed that non-equilibrium intermetallic phases between grains are mainly Al0.5Fe3Si0.5, Al0.7Fe3Si0.3 and Al5Mn12Si7. After homogenization, the main residual phase is Al5Mn12Si7. Compared with single homogenization, two-stage homogenization can effectively reduce the homogenization time and is good for the precipitation of fined Al3(Er, Zr) particles.

Xiang Zhang, Hui Huang, Xiaoli Liu, Yifei Liu, Hongbo Wang, Shengping Wen, Kunyuan Gao, Xiaolan Wu
##### Effect of Intermediate Annealing Temperature and Aging on the Mechanical Properties and Conductivity of Al–0.2Mg–0.35Si–0.3Ce Wire Rod

The present study investigated the effect of intermediate annealing temperatures on the microstructure, mechanical properties and conductivity of Al–0.2Mg–0.35Si–0.3Ce wire rod, which experienced hot extrusion (named as E), cold drawing (named as D), annealing (named as A) and cold drawing, i.e. EDAD. And four intermediate annealing temperatures (150, 200, 250, 300 °C) were carried out for investigation. Microstructure observation shows that no recrystallization occurs in the wire rod when annealed at 150 and 200 °C. However, it occurs when the annealing temperature reaches 250 °C. Tensile tests indicate that the ultimate tensile strength (UTS) of the as-EDAD samples firstly increases to a maximum value of 218 Mpa when the annealing temperature increased to 150 °C, and then decreases dramatically with the temperature continuously increasing. However, the elongation and conductivity of the as-EDAD samples just go oppositely. The conductivity of the sample annealed at 300 °C reaches 57.1%IACS, which is about 3.3%IACS higher than that of the sample without annealing. The effect of aging (190 °C for 20 h) on the mechanical properties and conductivity of as-EDAD samples was also investigated. Results show that the variation trend of UTS, elongation and conductivity of the EDAD-aging samples is similar to that without aging. The UTS decreases after aging, however, elongation and conductivity both increase.

Yuna Wu, Hengcheng Liao, Jianfeng Zhang
##### Quantitative Investigation of Precipitates in a High-Zinc Al–9.54Zn–2.10Mg–1.69Cu Alloy with Various Typical Tempers

In order to analyze single stage ageing behavior of a high-zinc Al–9.54Zn–2.10Mg–1.69Cu alloy, the microstructure of the alloy subjected to T6, T76 and T77 states are investigated via transmission electron microscopy (TEM) combined with high-resolution transmission electron microscopy (HRTEM) attached to it. Under the premise in precipitate observations, diameter distributions and average diameter size of precipitates are deduced from Bright-Field TEM (BF TEM) images projected along $$\left\langle {110} \right\rangle_{\text{Al}}$$ orientation with the help of an image processing. The results indicate that the main precipitates are GPII zone and η′ phase in the T6 and T77 alloys while η′ and η phase in the T74 alloy. The Bright field TEM observations reveal that the matrix precipitates for the T6 and T77 alloys have small size and dispersive distribution while that for the T74 alloy has big size and sparse distribution. Quantitative precipitate characteristics including diameter distribution and average diameter size have been gained by an image processing relying on BF TEM images projected along $$\left\langle {110} \right\rangle_{\text{Al}}$$ orientation. The results reveal that the T6 and T77 alloys have more than a half percentage of precipitates with a size less than 2 nm while the T77 and T74 alloys have broad precipitate distribution range till 14 and 16 nm, respectively. The grain boundary precipitates (GBPs) for the T6 alloy have continuous distribution with small size while that for the T74 and T77 alloys distribute intermittently with big size.

Kai Wen, Bai-Qing Xiong, Yong-An Zhang, Xi-Wu Li, Zhi-Hui Li, Shu-Hui Huang, Li-Zhen Yan, Hong-Wei Yan, Hong-Wei Liu
##### Flow Behaviors and Corresponding Constitutive Equation of the Al–9.4Zn–1.9Mg–2.0Cu Alloy

Isothermal compression tests of the Al–9.4Zn–1.9Mg–2.0Cu alloy were carried out at the temperature ranging from 300 to 460 °C and the strain rate from 0.001 to 10 s−1, and the deformation degree was 70%. Flow stress curves show that the flow stress decreases with the increasing deformation temperature and the decreasing strain rate. The measured flow stress was corrected because of the effect of friction. The corresponding corrected stress values are lower than measured stress values. The effect of friction is far greater when hot-deformations occurred at lower temperatures or higher strain rates. A constitutive equation considering the effect of strain on material constants (i.e. α, n, Q and A) are established based on the Arrhenius-type equation. Compared with the experimental results, the flow stresses calculated by the constitutive equation have a high precision with the correlation coefficient of 0.95. Results show that higher deformation temperatures and lower strain rates are beneficial for hot deformation of the Al–9.39Zn–1.92Mg–1.98Cu alloy.

Guohui Shi, Yong’an Zhang, Xiwu Li, Zhihui Li, Shuhui Huang, Lizhen Yan, Hongwei Yan, Hongwei Liu
##### Effect of RRA Treatment on the Properties and Microstructural Evolution of Al–Zn–Mg–Cu–Er–Zr Alloy

Effect of RRA treatment on the mechanical properties and microstructure of Al–Zn–Mg–Cu–Er–Zr aluminium alloy was researched by hardness measurement, conductivity measurement, exfoliation corrosion measurement, transmission electron microscopy (TEM). Discussed the relationship between the regression treatment and composite properties of the alloy. The study found that the hardness of RRA treated alloys first rise and then decline with the increasing of regression time, but the corrosion performance is increasing all the time. After pre-aging treatment 120 °C/24 h, regression treatment 180 °C/60 min, re-aging treatment 120 °C/24 h, the combination property of the alloy is optimal, the hardness, conductivity and the exfoliation corrosion grade are respectively: 207.6 HV, 33.53%IACS, PC. At this moment, it is found from the TEM observations that the matrix precipitates are small and dispersed, resemble to T6 temper. The grain boundary precipitation out phases are discontinuous distribution and the relatively wider PFZ, similar to the T73 temper.

Xiaofei Wang, Zuoren Nie, Hui Huang, Shengping Wen, Kunyuan Gao, Xiaolan Wu
##### Composition Optimization Study on 7N01 Aluminum Alloy

The effect of Mn, Mg, Zn and Zr elements on the microstructure and mechanical properties of 7N01 aluminum alloy was studied by hardness, electrical conductivity, tensile test, optical microscopy (OM) and scanning electron microscopy (SEM), which was based on the optimal extrusion and heat treatment process. Results show that a new alloy with optimum properties combination is found and its composition is Al–4.6Zn–1.55Mg–0.6Mn–0.15Cr–0.1Zr–0.03Ti (wt%), of which ultimate tensile strength and yield strength are 421.3 and 369.2 MPa respectively, and the phases are (Fe, Mn)Al6, η(MgZn2) and a small amount of η′(MgZn).

Wenlin Gao, Gang Sun, Qingmei Ma, Changde Lu, Xiangjie Wang, Xianpeng Ni, Jianzhong Cui
##### The Correlation Between Structure and Performance of Advanced 2219 Aluminum Alloy

This study aimed to explore the correlation among forging process, structure and mechanical performance of advanced 2219 aluminum alloy forged ring. The microstructure of the alloy forged ring in tangential, radial and axial were analyzed by Optical microscope (OM), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) test. The results show that the microstructure of 2219 aluminum alloy forged ring is a plate-like structure and the precipitation phases distributed along the rolling direction. Among which, fine Al2Cu particles uniformly distribute in the grain. The hardness and tensile performance of the forged ring in the tangential, radial and axial directions was tested. The results indicate that the hardness perpendicular to the axial plane is 153.7HV, and the tensile performance of the alloy along the tangential direction is the highest. By observing the microstructure of the fracture, it is founded that the dimple in the tangential is deeper and smaller, and the elongation in tangential are higher than those in the axial and radial. The UTS (ultimate tensile strength) of the forged ring is more than 400 MPa, and the YST (yield tensile strength) is more than 300 MPa. an elongation of more than 10% is obtained. No anisotropy is found on both the microstructure and mechanical performance. The results indicate that the 2219 aluminum alloy forged ring can be applied on the multi-directional bearing structure parts.

Ningning Jian, Lihua Chai, Zhilong Chang, Guodong Shi, He Li, Tounan Jin, Ziyong Chen, Haijing Wang
##### Effect of Yield Function on the Stamping Springback of Aluminum Alloy

The springback of aluminum alloy sheet after stamping is much larger than that of the steel sheet of the same strength. This is one of the reasons for the aluminum alloy sheets not yet being widely used in stamping automobile parts. The quality of springback prediction for a sheet metal forming process depends on a precise material model. In this paper, an A-pillar was selected as an example to investigate the effect of yield function (Hill’48, Barlat89 and Barlat2000) on the predicted springback of automotive parts pressed from the 5754 aluminum alloy sheet. A finite element model was established using commercial stamping software PAMSTAMP2G. The parameters of the material models were derived from the uniaxial and biaxial tensile tests. The stamping experiments of A-pillar were carried out to obtain the springback values of actual parts. The springback values of the stamped parts were measured by the 3D scanning technology. The comparison between the predicted values and experimental ones shows that the predicted springback using the Barlat2000 yield function is the best.

Mingdong Huang, Lei Fu, Li Lee, Cheng Liu
##### Effect of Solution Treatment and Aging Treatment on Microstructure and Properties of 1953 Aluminum Alloy Pipe

Aluminum drill pipes have low density, high specific strength and good stress corrosion resistance, possessing a huge application potential in the oil drilling. The 1953 alloy belongs to the Al–Zn–Mg–Cu alloy, and it is one of the most promising aluminum alloy materials for petroleum drill pipe. In this paper, the 1953 aluminum alloy were studied by hardness tests, conductivity tests, tensile tests, optical microscope and scanning electron microscopy. The results show that there are a large number of AlZnMgCu phases and a small amount of Fe and Si impurity phases after extrusion. After the solution treatment, the AlZnMgCu phases have been dissolved, and the residual phases in the alloy are mainly impurity phases with Fe and Si. The comprehensive performance is excellent after solution treatment at 440 °C/1 h + 470 °C/1 h and aging treatment at 120 °C/24 h. The hardness, electrical conductivity, yield strength, tensile strength and elongation can reach 191.2 HV, 18.9 MS/m, 578 MPa, 620 MPa, and 11.2%, respectively.

Yanjun Fu, Xiwu Li, Shuhui Huang, Zhihui Li, Hongwei Yan, Lizhen Yan, Hongwei Liu, Yongan Zhang, Baiqing Xiong
##### Influence of Cooling Intensity Difference Between Upper and Lower Surface to the Residual Stress Distribution of 7050 Aluminum Alloy Plates

Residual stress of aluminum alloy thick plates causes distortion in subsequent machining operations for aircraft components. During spray quenching the different cooling rates applied across the plate thickness to produce residual stresses. If differential cooling is applied to the upper and lower surfaces, this could lead to an asymmetric distribution of residual stress on both sides of plate. This in turn causes potentially uncontrollable part distortion and dimensional inaccuracy during the machining operation. In this study, a finite element (FE) model, taking into account of the different cooling intensity on the upper and lower surfaces, was established to predict the residual stress. Residual stress was measured using an ultrasonic stress measuring apparatus. The results showed that the residual stress on the upper surface was −174 MPa when the applied water flux was 350 m3/h, and −194 MPa on the opposite surface where the corresponding water flux was 300 m3/h. This was found to be in good agreement with the simulation results. It was found that the residual compressive stress on the surface with the higher cooling intensity was smaller than the side with lower intensity which is contrary to conventional wisdom. Therefore, based on the difference of cooling intensity on the two surfaces, the guidance for utilizing the roller-quenching-equipment can be derived finally.

Junqiang Wang, Guanmei Niu, Zhongyu Yang, Hailong Cao, Cheng Liu
##### Effect of Solution Treatment on the Microstructure and Fatigue Properties of 7050 Aluminum Alloy

The primary requirement of aircraft design is safety. The fatigue fracture is difficult to detect and prevent, which is a major safety hazard during aircraft service. In this paper, the influence of solution heat treatment on the microstructure and resistant of fatigue crack growth of 7050 alloy is investigated. For one-stage solution heat treatment, with the solution temperature increases, the area fraction of the coarse constituent phase decreases and the recrystallization fraction increase, and conresponsively the strength and fracture toughness increase and the fatigue crack growth rates decrease. Under the two-stage solution heat treatment, the alloy has the best fatigue crack growth resistance compare with the one-stage solution heat treatments. The effect of solution heat treatment on the properties can be understood on the basis of the combined influence of the constituent phase and the recrystallized fraction.

Xiang Xiao, Wei Li, Jian Zhao, Cheng Liu
##### Effect of Zr Addition on Localized Corrosion Behavior of Al–Zn–Mg Alloy

The effects of Zr addition on localized corrosion resistance of Al–Zn–Mg alloy were investigated by means of intergranular corrosion (IGC) immersion and exfoliation corrosion (EXCO) immersion tests. The mechanism was discussed based on microstructural characterization by optical microscopy (OM) and scanning transmission electron microscopy (STEM). The results showed that Al–Zn–Mg–Zr alloy exhibited a smaller intergranular corrosion depth and exfoliation corrosion depth than Al–Zn–Mg alloy. Zr inhibited recrystallization and refines grains. The subgrain boundaries could retard the propagation of corrosion. Compared with Al–Zn–Mg alloy, Al–Zn–Mg–Zr alloy has lower Zn and Mg content of the grain boundary precipitates and narrower precipitate free zone near grain boundaries.

S. D. Liu, W. R. Chai, Q. Wang, Q. L. Pan, A. D. Li, Y. L. Deng, X. M. Zhang
##### Preparation and Corrosion Performance of Silane/Ce Films on 7N01 Aluminum Alloy

The protective bis-[triethoxysilylpropyl]tetrasulfide (BTESPT) silane films doped with cerium were prepared on surface of 7N01 aluminum alloy by dip-coating method. Single variable tests were used to obtain optimal silane concentration, curing temperature and cerium salt concentration. Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscope (SEM) were used to characterize structure of the formed films. Corrosion performance of the films was evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and soaking tests. The results show that the corrosion resistance of the silane film on 7N01 aluminum alloy is improved greatly by doping of Ce into the silane film. The proper silane volume fraction is 5% and the curing temperature is 100 °C. The optimum cerium nitrate doping into the silane solution is 5 × 10−3 mol/L.

Sha Peng, Lin Sun, Hua-qiang Lin, Yun-lai Deng, Ming-an Chen
##### Analysis on Causes of Flaring Cracks in Thin-Walled 5A02 Aluminum Alloy Tubes

In flaring process of some thin-walled 5A02 aluminum alloy tubes (“the tubes”) upon cold rolling and annealing, longitudinal cracks occur at the flared ends. In order to figure out the reason for these flaring cracks, observations and experiments are conducted on the cracks at flared ends by means of macroscopic examination, metallurgical microscope, scanning electron microscope, energy spectrometer and electronic universal testing machine. The experimental results show that for the tubes with flaring cracks, both the grain size and the difference among grain sizes are large. The distribution of second phase particles is nonuniform and aggregation of precipitation phase exist. The cracks nucleate and propagate under stress in regions where the inclusions are located. The defects, such as scratches and pitting, existing on the inner surface of the tubes, cause the nucleation and propagation of cracks in the defect regions under stress.

Chuan Wang, Defu Li, Jie Hu, Guoqiang Chai, Shengpu Liu, Zuoming Sun
##### Effect of Quenching Rate on the Exfoliation Corrosion of 7020 Aluminum Plate

The exfoliation corrosion resistance of 7020 aluminum plate treated with different quenching rates after solution treatment was investigated through standard exfoliation corrosion (EFC) immersion tests combined with scanning electron microscopy (SEM). The results showed that the EFC resistance of this alloy plate decreased with the decrease of quenching rate. The corrosion rank ranged from EA to ED, and the maximum corrosion depth ranged from 388 to 570 μm.

ShengDan Liu, Chen Guo, ZhenShen Yang, HuaQiang Lin, Lin Sun, YunLai Deng, XinMing Zhang
##### Healing of Double Oxide Film Defect Under Holding Pressure in A357 Alloy

The bonding possibility of the double oxide film defect was investigated by holding pressure during solidification after holding in liquid A357 alloy for 13 min. The defect was modeled experimentally through contacting the oxide film layers of the A357 alloy. The composition and morphology of the oxide film layers were studied by SEM and EDX. The results show that the bonding area of the oxide layer increased with the holding pressure during solidification. This is due to the extrusion ability among the porous spinel gets stronger with the increase of holding pressure, which means the liquid metal, could flow through the porous spinel much easier.

Shanguang Liu, Chuanbiao Luo, Guoai Li, Zheng Lu, Shenglong Dai
##### Enhancing the Impact Toughness of ADC12 Aluminum Alloy by Alloying with Y and Solution Treatment

Microstructures and phase compositions of as-cast and solution-treated ADC12 and ADC12-0.85Y alloys were studied by optical microscope, scanning electron microscopy and X-ray diffraction method. Meanwhile, the impact toughness was tested. The results showed that as-cast microstructure was refined significantly when 0.85%Y was added into ADC12 alloy. The coarse primary α-Al dendrite changed into fine cellular and equixed grains, and the Si-rich phase changed from long needle or plate to short rod or globosity. Meanwhile, few acicular new phase Al3Y precipitated. When the two alloys were solution-treated at 793 K for 8 h, the phase compositions did not change and the partial second phases dissolved into α-Al matrix. However, the long needle or plate Si-rich phase disappeared completely, and the remaining second phases precipitated by short rod or globosity. Meanwhile, the segregation degree between dendrites decreased. When 0.85%Y was added, the impact toughness value increased from 3.8 J/cm2 for as-cast ADC12 alloy to 10.8 J/cm2, and further reached 21.9 J/cm2 after the solution treatment, with the amplitude of 476% compared with the corresponding as-cast value of ADC12 alloy. The impact fracture exhibited the typical ductile fracture with dimples.

Zhenghua Huang, Yi Yao, Wenjun Qi, Chunjie Xu, Zhongming Zhang, Yangde Li, Weirong Li
##### Effects of Mn Content on Microstructure and Hardness of 6061 Aluminum Alloy

Microalloying is an effective way to improve material properties. By means of scanning electron microscope/energy spectrum, X-ray diffraction, metallographic analysis and hardness tests, the effects of microalloying element Mn on as-cast, homogenization, aging microstructure and hardness were investigated in the basic of 6061 aluminum alloy. The results showed that the as-cast 6061 alloy consisted of the primary Al, the irregular strip-shaped Al8(FeMn)2Si phases, fishbone-shaped Al5(FeMn)Si phases and Mg2Si phases. Through microalloying, the morphology of phases transformed from irregular strip into fishbone obviously as Mn content increased. After homogenization process, Mg2Si phase dissolved into the alloy matrix but iron-rich phase cannot. With the increase of Mn content, the phase transformation of fishbone-shaped Al5(FeMn)Si to particle-shaped Al8(FeMn)2Si occurred. During solution-aging treatment, higher Mn content could promote the precipitation of stable phase β(Mg2Si). Mn had a significant effect on the morphology of the crystalline phases which had a direct influence on the hardness of aluminum alloy. It was found that the addition of 0.24 wt% Mn to 6061 aluminum alloy could make the as-cast and aging alloys achieve the maximum hardness value 67 and 105 HBW, respectively.

Xingyu Ding, Yongqi Cheng, Peng Zhang, Yong Dong, Zhengrong Yao, Peisong Jiang
##### Microstructural Evolution During Homogenization Heat Treatment for an Al–0.92Mg–0.78Si–0.60Zn–0.20Cu–0.12Zr Alloy

Homogenization heat treatment on an Al–0.92Mg–0.78Si–0.60Zn–0.20Cu–0.12Zr alloy was investigated by OM (optical microscopy), DSC (differential scanning calorimetry), energy dispersive X-ray diffractometry (EDX), and SEM (scanning electron microscopy) in the present work. The results indicated that with homogenization temperature increasing, the grains enlarged and the secondary phases dissolved into matrix gradually. The residual phase was Fe-rich particle after the alloy homogenized at 550 °C for 24 h and Zr-containing particle with larger size precipitated. While grains of the alloy with almost no change were observed after double-stage homogenization treatment, and the phases dissolved into matrix completely and Zr-containing particle with smaller size precipitated. Meanwhile the size of Zr-containing particle changed little with prolongation of second-stage time. The ideal homogenization process for the alloy was to homogenized at 430 °C for 10 h, subsequently followed by 550 °C for 24 h.

Lizhen Yan, Yong-An Zhang, Baiqing Xiong, Xiwu Li, Zhihui Li, Hongwei Liu, Shuhui Huang, Hongwei Yan, Kai Wen
##### Microstructure and Stress Corrosion Behavior of MIG Welded Joint Al–Zn–Mg Alloy

The microstructures and stress corrosion behaviors of the welded joint in a MIG welded Al–Zn–Mg alloy were investigated by slow strain rate test and OM, EBSD, TEM observation. The results indicated that the stress corrosion cracking index of welded joint is bigger than the base metal, which means the stress corrosion resistance of base metal is better than MIG welded joint. The stress corrosion of MIG welded joints mainly occur in the weld zone and heat affected zone, which indicates that they are the weak areas of welded joints. The fracture mode of the joint in 3.5% NaCl solution are intergranular brittle fracture and partial transgranular dimple fracture, while that of base metal is only transgranular dimple fracture. The microstructure is coarse equiaxed grain in welded zone, and there is virtually no strengthening phase in this zone. In the fusion zone, fine columnar grains and equiaxed grains are distributed at different sides. There is the fibrous phase in the base metal, and the microstructure of heat affected zone is similar to this zone. But in the heat affected zone, recrystallization occurs and the grains grow obviously. And the strengthening phases in the quenching zone are completely dissolved, but their particles in over aged zone became coarseobviously.

Lingying Ye, Wenqing Yang, Chuqi Jiang, Huaqiang Lin, Shengdan Liu, Jianguo Tang, Yunlai Deng, Xinming Zhang
##### Coarse Grain Layer on Stress Corrosion Cracking Resistance of Al–Zn–Mg Alloy

The correlation between chemical composition, multiphase microstructure and stress corrosion performance of Al–Zn–Mg alloy with different thickness coarse grain layers was studied by optical microscopy (OM), scanning electron microscope (SEM), transmission electron microscopy (TEM), tensile test and four point bending stress corrosion performance test. The results indicated that the thickness of coarse grain layer of three kinds of Al–Zn–Mg alloy profiles used in the test were about 200, 400 and 900 μm, while the stress corrosion cracking (SCC) resistance and strength of specimens with coarse grain layer decreased with increase of coarse grain layer thickness. Among different profiles, the stress corrosion cracking resistance of specimens with coarse grain layer and center layer without coarse grain layer exhibited the difference with the change of coarse grain thickness.

Lingying Ye, Xuebin Yao, Huaqiang Lin, Shengdan Liu, Yunlai Deng, Xinming Zhang
##### Effect of RRA Treatment on the Microstructure and Fatigue Behavior of 7020 Aluminum Alloy

The fatigue crack growth (FCG) behavior and fatigue strength of 7020 aluminum alloy in an over aged treatment and two retrogression and re-aging (RRA) treatments were investigated. The microstructures and fractographies were observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The result showed that RRA-treated alloys have faster FCG rate than over aged alloy at lower ΔK region due to the dense non-shearable precipitates. And the RRA120 alloy re-aged at 120 °C/24 h has a relatively faster FCG rate than RRA150 alloy re-aged at 150 °C/12 h. RRA-treated alloys have higher fatigue strength than over aged alloy. The fatigue strength corresponding to 107 cycles of over aged, RRA120 and RRA150 conditions are 114, 129 and 118 MPa, respectively. The effect of RRA treatment on the fatigue property is mainly caused by its finer and more dispersed precipitates and narrower precipitate free zone (PFZ).

Yong Wang, Yunlai Deng, Shengdan Liu, Zhaojun Shan, Jianguo Tang, Xinming Zhang
##### Static Recrystallization Grain Size Model of 5083 Aluminum Alloy

The influence of material initial grain size, deformation temperature, strain rate and true strain on the static recrystallization grain size of 5083 aluminum alloy after hot deformation was studied by thermal compression test with Gleeble-3800 simulated machine. The grain size model of static recrystallization of 5083 aluminum alloy was established according to the experimental results. The results show that the static recrystallization size of 5083 aluminum alloy decreases with the increase of true strain or strain rate, and increases with the increase of deformation temperature or original grain size, and the true strain has the greatest effect. The predicted value of the static recrystallized grain size model exhibits a good agreement with the experimental data.

Qingsong Dai, Yunlai Deng, Lingying Ye, Xu Liu, Weihua Zhao
##### Measurement of Residual Stress in As-Quenched 7055 Aluminum Plate by Various Methods

The accuracy of different residual stress measurement methods has always been the research focus from the beginning of research on residual stress. In this study, both conventional and newly-developed methods were applied to measure the residual stress in as-quenched 7055 aluminum plate. Methods such as hole drilling, X-ray diffraction based on sin2Ψ and cos α approaches, crack compliance method and neutron diffraction method were used. In the meanwhile, finite element simulation was used to obtain the residual stress distribution as a comparison. The results showed that among the methods studied, X-ray diffraction method has the greatest test error due to its shallow test depth. However, if the measurement condition was well controlled, the error could be acceptable. The absolute values of residual stress obtained by X-ray diffraction method were slightly greater than hole drilling method. If calculated with the reasonably chosen crack compliance function, the test result was similar to neutron diffraction method. Under different quenching conditions, all the studied methods showed that the greater the quenching cooling rate, the greater the absolute value of residual stress.

Hongwei Yan, Xiwu Li, Zhihui Li, Ya’nan Li, Shuhui Huang, Lizhen Yan, Yong’an Zhang
##### Single Stage Ageing Property and Precipitation Variation of a High-Zinc Al–Zn–Mg–Cu Alloy

In order to analyze single stage ageing behavior of a high-zinc Al–Zn–Mg–Cu alloy, the microstructure and property variations of the alloy treated by various temperatures were explored by hardness, conductivity, tensile properties, transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM) techniques. The results indicated that a long time was needed to reach a peak hardness value for the alloy treated at 100 and 120 °C and the peak hardness value could sustain a relatively long time interval. The alloy treated at 120 °C adopted a shorter time to reach peak hardness values and its peak hardness value was larger compared with that at 120 °C. The hardness treated at 140 °C reached the peak rapidly and then diminished continuously. With ageing time prolonging, the conductivities of the alloy treated at various temperatures increase persistently. After a peak ageing regime of 120 °C/24 h, the alloy possessed fine and dispersedly distributed matrix precipitates (MPs) and the ultimate tensile strength (UTS), yield strength (YS), elongation and electrical conductivity were 697 MPa, 655 MPa, 12.9% and 17.3 MS m−1, respectively. With the alloy temper varying from under-ageing to peak-ageing to over-ageing, the variety of MPs changed from GPI zone, GPII zone and η′ phase to GPII zone and η′ phase to η′ phase. During this process, the size distribution of MPs became broader and average precipitate size became larger.

Yun-Qiang Fan, Kai Wen, Zhi-Hui Li, Xi-Wu Li, Yong-An Zhang, Bai-Qing Xiong, Jian-Xin Xie
##### Classification and Evolution of Porous Defects in Spray-Formed Al–Zn–Mg–Cu Alloy

The porous defects classification in spray-formed Al–Zn–Mg–Cu alloy was investigated in this paper during spray forming, hot isostatic pressing (HIP) and homogenization. Metallographic microscopy and scanning electron microscopy (SEM) were used to study the microstructure and porous defects. The results showed that, there were four kinds of porous defects in spray-formed alloy, which were distinguish by the reasons of formation and shape. The first kind, the second kind and the third kind porous defects contain gas, while the forth kind porous defect did not contain gas. The forth kind porous defects can be eliminated by HIP, but the other three only can be compressed to be smaller. After homogenization, the porous defects with gas grew up and was observed easily again, unless some porous defects connected with ingot surface through the other porous defects which could exhaust gas during HIP. The second phase in the ingot restored back mostly after the homogenization treatment of 440 °C/12 h + 474 °C/48 h.

Shuhui Huang, Hongwei Liu, Zhihui Li, Baiqing Xiong, Yongan Zhang, Xiwu Li, Hongwei Yan, Lizhen Yan
##### The Influence of Homogenizing of 6351 Aluminum Alloy on the Heating Method of Extrusion

This paper studies the influence of different homogenizing process on the heating method of extrusion by means of metallographic microscope and eddy current conductivity meter. The results show that there are a large number of rich-Fe/Mn particles in 6351 alloy matrix by homogenizing in 560 °C. The rates of cooling after homogenizing have little effect on the long-time heating and heat-preservation heating before extrusion. The method of heating at a temperature higher than 500 °C before extrusion and then cooling in air is beneficial to the low-temperature and high-speed extrusion of 6351 alloy. If the total time of heating and extrusion is within 10 min, the samples which cool rapidly after homogenizing can be extruded at low-temperature and in a high-speed with the eddy-current heating.

Li Wan, Yunlai Deng
##### Effect of Zr Content on Microstructure and Mechanical Properties of Al–Mg–Si–Cu Alloy

Effect of Zr content on microstructure and mechanical properties of Al–Mg–Si–Cu alloy were investigated by means of metallograph microscope, tensile test and transmission electron microscopy (TEM). The results show that the main precipitate is AlCuMgSi phase in Al–Mg–Si–Cu alloy after cold rolling. Zr element plays a dominant role in refinement of grains. With the increase of Zr content, numerous dislocations are found in Al–Mg–Si–Cu alloy, together with a large amount of complex phase containing Zr element precipitate within the grains. When the content of Zr is 0.7%, the tensile strength and elongation of Al–Mg–Si–Cu alloy are 490 MPa and 10%, respectively.

Y. P. Sun, X. H. Zhou, W. B. Xu, J. M. He, W. X. Wang
##### Effect of Upsetting and Cogging Technique on Microstructure and Mechanical Properties of β Titanium Alloy

The effect of upsetting and cogging Technique on Microstructure and mechanical properties of β-CEZ and Ti-38644 titanium alloys is studied in this paper. The results showed that β grain boundaries are not distinct and lath-shaped α phases precipitate in grains, for the β-CEZ and Ti-38644 alloys with single upsetting and cogging under the transus temperature. The grains are relatively coarse and their sizes are non-uniform. While for the β-CEZ and Ti-38644 alloys with multiple upsetting and cogging, the equiaxed microstructure become fine and uniform. β grain boundaries are very clear and small acicular and lath-shape α phase also precipitate in the equiaxed grains, and the microstructure difference is small between along transverse direction and longitudinal one. The multiple upsetting and cogging can significantly improve the reduction of area and the mechanical properties of β-CEZ and Ti-38644 titanium alloys with the refined and uniform grains.

Yunlian Qi, Liying Zeng, Xiaonan Mao, Shewei Xin, Liu Wei, Huamei Sun
##### Effect of Thermo-Mechanical Deformation on the Microstructure Evolution in a High Temperature Ti Alloy with Erbium

The effect of thermo-mechanical deformation on the microstructure was investigated by isothermal compression and microstructure characterization. The mechanical response of as-casted Ti–6.2Al–3Sn–5Zr–0.5Mo–1.0Nb–0.4Si–0.2Er titanium alloy was sensitive to the deformation temperatures and strain rates. The true stress increased with the increase in the strain rate and decreased in temperature. The discontinuous dynamic recrystallization of β phase was promoted with the increase in temperatures. Global α phase generated during the deformation at a temperature of 980 °C. The (Ti, Zr)3Si and participated phase were dissolved into the matrix above 950 °C, which acted as the homogenizing annealing process. However, novel participated phases with an average diameter of 20 nm generated.

Tongbo Wang, Bolong Li, Xu Qiao, Peng Qi, Zuoren Nie
##### Thermal Stabilities of Ti-600 Alloy Pancake

Thermal stabilities at ambient temperature were studied on Ti-600 alloy before and after being exposed at 600 °C for 100 h. Fractography morphologies were investigated, and fracture mechanism analyzed. The results indicated that the strength of the alloy sample after thermal exposure decreased 1% or so, the elongation decreased about 49%, indicating that the plasticity decreased abruptly during the exposure process. For the as-solutioned plus as-aged samples, the cracks originate from the center of the fracture, dimple typed fracture can be found in the fractographies. After thermal exposure, only cleavage facets can be observed in the fractographies, the fractures propagate along the interfaces of lamellar α phases. The fractography of the tensile specimen prior to and after thermal exposure presented the feature of intergranular fracture, transgranular plus intergranular rupture, respectively. These results are caused by the precipitation and the existence of the brittle oxidizing layers. The cracks formed in the oxidizing layers first and then propagated into the matrix during the tensile tests. Oxygen filtration in the surface layer was one of the important reasons for the decrease of plasticity. The major deformation mechanism for Ti-600 alloy without and with thermal exposure is dislocation slips pass-through α bundles, α/β phase boundary slips during the tensile deformation process at ambient temperature, respectively.

Liying Zeng, Xiaonan Mao, Quan Hong, Yunlian Qi, Yongqing Zhao
##### Microstructure and Properties of Large Diameter Elbow of Ti75 Titanium Alloy with Short Radius Made by Expanded-Diameter and Pushed-Bend Method

The elbow made by expanded-diameter and pushed-bend method is feasible. Under the action of pushing force, expanding-diameter and bending moment of horn mould, the elbow generates composite deformation including bending and compressing deformation along axial direction and off-center expanding-diameter deformation along circumferential direction. The expanding-diameter deformation reduces wall thickness, while the compressing deformation of belly is greater than that of back, and result in thickening wall thickness on belly and eccentricity. The wall thickness flowed from belly to back along two sides of horn mould during expanding-diameter to compensate for thinned wall thickness on back of elbow during off-center expanding-diameter. The wall thickness uniformity of elbow was related to design of horn mould, pushing temperature and temperature field and pushing rate. The temperature of Ti75 titanium alloy elbow made by expanded-diameter and pushed-bend method was chosen in two phase region. It can reduce the deformation resistance and improve the alloy plasticity, and the elbow keeps the properties and microstructure consistent with pipe. The elbow made in β phase region easily produce grain over burning and overgrowing. The annealing of Ti75 titanium alloy elbow can be selected in two phases, which can keep elbow strength and microstructure homogenization.

Jun Chen, Tingxun Wang, Yu Du, Haiying Yang, Wei Zhou, Shewei Xin, Qian Li
##### Fatigue Behavior and Failure Analysis of Ti-6Al-4V Forging with High Oxygen Content

The microstructure, texture and HCF (high cycle fatigue) behavior of a Ti–6Al–4V forging with 0.20 wt% oxygen were investigated. The material was composed of 80 vol% of equiaxed αp grains and 20 vol% of transformed β (βT). Average size of the αp phase was about 14 μm. EBSD analysis indicated a weak basal texture with intensity of 2 times random. The forging billet exhibited a good combination of ductility and strength performance and the mechanical properties did not show obvious anisotropy. The fatigue life had a large scatter and the mean life increased as the stress level decreased. The minimum life and POF = 0.1% life of the samples increased with the decrease of stress level. The difference of the feature of facets at the fatigue crack initiation region is considered to be the main cause of fatigue life scatter. The formation of the faceted area in fatigue crack initiation area results from the nucleation site of fatigue crack located in grain clusters with similar orientation.

Yunxi Liu, Wei Chen, Zhiqiang Li, Bin Tang, Gang Yao
##### Effects of Er and Re on the Microstructure and Mechanical Properties of a New High Temperature Titanium Alloy

In order to further improve the usage temperature of high temperature titanium alloy, two kinds of near α titanium alloy ingots with Er and Re were prepared. The influences of Er and Re on the alloy under two kinds of forging conditions, namely, β phase region and near β phase region were investigated by scanning electron microscopy (SEM) and tensile test. The results showed that under the forging in β phase region both basket-weave microstructure and there are obvious beta grain boundaries in the structure. The equiaxed α of the alloy containing Re is more obvious after forging in near β phase region. The overall performance was better when forging in near β phase region than in β phase region, the comprehensive properties of the alloy that containing Re was better than that of Er.

Yanfang Jin, Lihua Chai, Dandan Li, Zongyue Feng, Guodong Shi, Tounan Jin, Ziyong Chen
##### Analysis of Friction and Wear Behavior of Vacuum Nitriding on Ti80 Titanium Alloy

Titanium alloy has light weight, low young modulus, small coefficient of thermal expansion and good corrosion resistance properties. Especially for high corrosive hydrogen sulfide and carbon dioxide, titanium alloy shows excellent resistance. With the replacement of Ni based alloy with titanium alloy, titanium oil pipes have become one of the development directions of high temperature and high pressure wells. Recently, the titanium alloy tubing has been used in Yuanba gasfield, indicating that titanium alloy tubing has entered a practical stage in China. However, because of the low hardness, high friction factor, poor wear resistance, serious adhesive wear, the erosion of crude oil and the friction of the sucker rod have a great influence on the wear properties of the titanium alloy tubing. These deficiencies will become one of the main constraint factors for the development of titanium alloy oil tubes. In order to solving this problem, in the present paper we improved the tribological performance by means of ion nitriding on Ti80 alloy. The microstructure, surface morphology, hardness tester and wear resistance of the material were analyzes by means of XRD, SEM, Vickers hardness tester and wear and abrasion tester. The results showed that the tribological performance of Ti80 alloy oil tubes is improved by ion nitriding process.

Lei Li, Xiaonan Mao, Quan Hong
##### Effect of NaOH Concentration on the Microhardness and Corrosion Resistance of Titanium by Acid-Hydrothermal Method

To enhance the microhardness and corrosion resistance of modified pure titanium, TiO2 nanostructure has been prepared on titanium substrate by acid-hydrothermal method. The morphology of the titanium surface underwent change from nanosheets to nanorods with the increase of NaOH concentration, which was performed by the scanning electron microscope (SEM). A mixture of the anatase TiO2 and rutile TiO2 were formed on the synthesized titanium surface measured by X-ray diffraction (XRD). Microhardness was measured by microhardness tester and the hardness rose sharply and then declined gradually as the increase of NaOH concentration, showing a considerably high hardness value of 361HV with NaOH concentration of 5 M (PAN-5). In addition, the corrosion resistance was examined in SBF by electrochemical methods. The polarization curve demonstrated that the corrosion resistance was optimal when the NaOH concentration was 5 M. Therefore, the hardness and corrosion resistance of titanium, with the appropriate morphology of nanorods, were optimized as the NaOH concentration was 5 M.

Ying Xu, Bian Wang, Yanqing Cai, Zizi Zhang
##### Effects of Forging Temperature on Microstructure and Mechanical Properties of 650 °C High Temperature Titanium Alloy

The microstructure and mechanical properties of the alloy Ti–Al–Sn–Zr–Mo–Nb–Ta–Si–C–Er forged at different temperature were discussed. The microscopic observation showed that both forged alloys consisted of basket weave structure, the alloy forged at 1000 °C had some lamellar α phase turning to equiaxed α phase, and its α lamellae was finer than that forged at 1050 °C, which coincided with the theoretical expectation. The mechanical properties at room temperature and 650 °C were measured, and the results showed that the forged alloy at 1000 °C possessed better mechanical properties. Compared with the alloy at 1050 °C, the alloy forged at 1000 °C has a high strength and slightly better elongation. The result showed that with the decrease of forging temperature, the strength and ductility increase, the size of α lamella reduces, and the number of equiaxed α phase increases. The excellent comprehensive mechanical properties of the alloy are obtained by forging at 1000 °C.

Dandan Li, Lihua Chai, Ziyong Chen, Tounan Jin, Guodong Shi, Yanfang Jin, Zongyue Feng
##### Forging Technology and Microstructure and Mechanical Properties of a Novel High Temperature Titanium Alloy Resistant to 650 °C

In this paper, the Ti–Al–Sn–Zr–Mo–Si series high temperature titanium alloy is designed by using the electron concentration theory and the first principles calculation. The ingot of a novel high temperature alloy was prepared by induction skull melting (ISM) in a water cooler copper crucible, then three different kinds of forging technology (two steps of axial forging, two steps of lateral forging and two steps of multi-directional forging) are employed for the Sub β forging at 1050 °C and the near β forging at 980 °C. It shows a basket-weave microstructure after sub β forging at 1050 °C. While after the near β forging at 980 °C, the alloy shows a duplex microstructure with a little amount of primary α-phase and mechanical properties is better than the alloy forging at 1050 °C. The grains undergoing a two steps of multi-directional forging is finer and more uniform, and the properties is more excellent for the alloy.

Zongyue Feng, Lihua Chai, Ziyong Chen, Tounan Jin, Guodong Shi, Yanfang Jin, Dandan Li
##### Failure Mode of Ductile Hole Formation in Thick Ti–6Al–4V Targets Having Equiaxed and Lamellar Microstructures

The 40 mm Ti–6Al–4V thick targets having equiaxed and lamellar microstructures were normally impacted by 12.7 mm and 14.5 mm arm-piercing projectiles. The Ti–6Al–4V targets having equiaxed microstructure showed better ballistic impact property compared with the Ti–6Al–4V targets having lamellar microstructure. The analysis of macro-damage and micro-damage features revealed that the failure mode of ductile hole formation in 40 mm thick Ti–6Al–4V targets should be divided into three stages: cratering, steady penetration and perforation. The role that adiabatic shear bands played varied in the different stages of penetration. In the stage of steady penetration, the plastic deformation was concentrated in adiabatic shear bands to coordinate with the squeezing into of the projectile. While in the stage of perforation, adiabatic shear bands were still failure paths for the formation of spalling fragments from the rear surface.

Chao Zheng, Xiurong Zhu, Haiying Xin, Zhiwen Shao, Huan Wang, Huaxin Peng, Xingwang Cheng, Fuchi Wang
##### Tribological Behavior of Graphene Reinforced 600 °C High Temperature Titanium Alloy Matrix Composite

Graphene reinforced high temperature titanium matrix composite synthesized by spark plasma sintering (SPS) was prepared from mixed powders of graphene oxide (GO) and 600 °C high temperature titanium alloy (TA29). SEM, EDS, XRD, Raman spectroscopy, UMT and SRV tribotester were employed to investigate the microstructure and tribological properties. Microstructural studies indicated that the added graphene oxide was substantially decomposed into graphene during the sintering process and did not cause a significant increase in oxygen content of the TA29 matrix. Graphene was observed to remain after the sintering process and be evenly dispersed in the TA29 matrix. The friction coefficient and wear rate under room temperature and light load were reduced by 15 and 60% respectively, because the graphene dispersed in the matrix was proved to improve the conditions of the frictional interface by self-lubricating effect. The wear rate under high temperature and heavy load was reduced by about 25% for the increasing in the yield strength of graphene reinforced TA29 matrix composite.

Mingyu Wu, Guangbao Mi, Peijie Li, Jianming Cai, Chunxiao Cao
##### In Situ Notched Tensile Fracture of TC21 Alloy with Different Microstructures

In order to investigate the notched toughness of TC21 alloy, different types of microstructures (lamellar, basketweave and equiaxed microstructure) prepared by different forging and heat treatment processes were studied. The microstructure was observed through the in situ SEM tensile technology. The cracks were found initiated along β grain boundary, lath α/β interface and equiaxed α/β interface. The crack easily propagate along the slip damage in the plastic area of the crack tip. The notched toughness of the TC21 alloy with the lamellar microstructure was found to be the highest among the three ones.

Hui Shao, Di Shan, Kaixuan Wang, Yongfeng Ding, Yunjin Lai, Guojun Zhang, Yongqing Zhao
##### Manufacture of Gr9 Titanium Alloy Tube for Small Size and Extra-Thin Wall

The Gr9 ϕ20 × 0.3 mm alloy tube with high-quality small size extra-thin walls was manufactured in this paper. The surface quality of the tube was improved by controlling the surface quality of the extruded tube and the intermediate tube and adjusting the clearance between the mandrel and the tube. The methods of controlling the rolling deformation and Q value and annealing temperature were adopted to solve the matching problem on comprehensive performance of Gr9 titanium alloy tube. The measure of controlling the tube size deviation and the rolling feed were taken to obtain high-precision finished tube. The result shows that the Gr9 titanium alloy finished tube manufactured by this process has high strength and high plasticity.

Shengchuan Chen, Xiuyong Li, Daoyu Xu
##### Effects of Different Cooling Methods on Microstructure and Mechanical Properties of TC4 Alloy

In order to investigate the influence of the microstructure obtained by different heat treatments on the mechanical properties, TC4 alloy were heated at 1050 °C for 5 min and cooled to room temperature through different cooling methods (furnace cooling, open-door furnace cooling, air cooling and water cooling). Subsequently, the microstructure was observed and the corresponding mechanical properties were measured. The experimental results showed that with the increase of cooling rate, the microstructure (α + β) became smaller and finer, and the rough tensile fractures gradually became flat; the elastic limit and tensile strength increased and the plasticity decreased. In the uniform plastic deformation stage, the plastic deformation power reached the maximum (43.50 MJ m−3) for air cooling. In the necking stage, the plastic deformation power was the maximum for furnace cooling and the static toughness reached 110.82 MJ m−3. TC4 alloy obtained good comprehensive properties in the case of furnace cooling.

Meigui Ou, Song Zhang, Hongchao Song, Yilong Liang
##### Relationship Between Diameter of Tensile Specimen and Grain Size for TA6V Castings

This paper studied the effect of wall thickness and specimen diameter on the mechanical property of TA6V castings. Grain size on the cross section of test pieces after testing was analyzed by optical metallography and fractography was observed by scanning electron microscopy. The results show that grain size grown up with the increasing thickness, meanwhile tensile strength and yield strength improved with the increasing thickness and specimen diameter. The diameter selection of tensile specimen should depend on the castings grain size. The crack initiates at the center of specimen and the fracture mechanism is brittle transcrystalline rupture.

Fuhui Gao, Min Li, Pan Ding
##### Oxidation and Hot Corrosion Behavior of Inconel 740H Alloy at High Temperature

The high temperature oxidation and high temperature sulfuration behavior of Inconel 740H alloy were studied by field emission scanning electron microscope (FESEM) and other equipments. The results show that the surface film formed by high temperature sulfuration of 740H alloy was looser and easier to fall off compared to surface film formed by high temperature oxidation. The oxide film obtained by high temperature oxidation contained two layers. The outer one was mainly composed of Cr2O3 and Ti2O3 phase, while the inner one was mainly composed of Al2O3 phase. The surface film obtained by high temperature sulfuration contained three layers. The outer one was mainly composed of Cr2O3 and Ti2O3 phase, the inner one was mainly composed of S and Cr compounds, and the middle one was mainly composed of inner oxide Al2O3. The depth of internal sulfuration zone increases as sulfuration temperature rises.

Kunjie Luo, Chengtao Li, Fei Xue, Yan Liu, Lu Zhang, Guodong Zhang
##### Failure Analysis on Perforation of Cr28Ni48W5 Alloy Heat Radiant Tube

An electric radiant tube in continuous annealing furnace was manufactured by using Cr28Ni48W5 heat resistant alloy with the built-in electric resistance bars of 0Cr27Al7Mo2 supported by the insulation of high-temperature ceramic disk. The radiant tube was found to be perforated during the annual routine inspection. In this study, a failure analysis of the radiant tube was performed by carefully visual inspection of the failed tube, scanning electron microscopy observation of perforation samples, and energy-dispersive X-ray spectroscopy analysis of the tube metals and oxide scales. The used materials were prepared by centrifugal casting. The analysis showed that there exhibited the microstructure characteristic of melting and solidification near the perforation hole, and the serious oxidation had occurred. It is inferred that under the condition of prolonged high-temperature heating, the creep deformation caused the electric resistance bar bend to contact the tube inner surface, and then electrical discharge took place and further melted the tube inner matrix through continuous heating by the release of electrical arc.

Jiazhi Tian, Guoli Zhai, Qingchao Tian
##### Desulfurization Mechanism of K4169 Superalloy Using CaO Crucible in Vacuum Induction Melting Process

The desulfurization experiments of K4169 superalloy were carried out in vacuum induction furnace with the thermodynamically stable CaO crucible. It was found that the sulfur concentrations did not change with the melting time when the melt mainly contained Ni, Cr, Fe and Nb element before Al or Ti addition. But the sulfur contents in the melt decreased rapidly to 6 ppm after 0.6% Al element addition. Adding Ti had a similar effect on desulfurization except for the ultimate sulfur content. The contact surface of CaO crucible with melt was studied using XRD, SEM and EPMA. The results showed that the distribution of sulfur element on the surface was coincident with calcium element. A small amount of calcium-aluminate (3CaO·Al2O3) and calcium titanium trioxide (CaTiO3) were detected at inner surface of crucible when Al and Ti were added into the melt respectively. About 20 μm depth layer of CaS desulfurization resultant was founded from the interface of the CaO crucible. The desulfurization reaction at interface are deduced to 3CaO + 2[Al]Ni + 3[S]Ni = 3CaS + Al2O3, and 3CaO + [Ti]Ni + 2[S]Ni = 2CaS + CaTiO3. In the condition of Al addition, 3CaO·Al2O3 is produced from Al2O3 and CaO crucible which has a low melting point and can be transferred easily, so it is the feasible reason to accelerate the desulfurization reaction greatly. Thermodynamics calculation and discussion about the reaction between the inner surface of CaO crucible and liquid metal has been done.

Kewei Xie, Bo Chen, Mengshu Zhang, Zhanhui Du, Xiangdong Zha, Shujiang Geng, Kui Liu
##### Microstructure and Solidification Characteristics and Segregation Behavior of Superalloy K4169

The solidification process and segregation feature of K4169 alloy is studied by DSC, Thermo-Calc simulation and isothermal solidification analyses. The segregation and precipitation behavior of superalloy K4169 during isothermal solidification at 1360 and 1120 °C have been observed by the means of optical microscopy (OM), electron probe microanalysis (EPMA), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results stated that the solidification began with the formation of primary γ dendrites, and accompanied by the formation of MC carbides. During the solidification, Nb, Mo and Ti were enriched in the residual liquid phase, which eventually lid to the formation of MC carbides and Laves phases. The liquidus of K4169 was 1354 °C, and the solidus was 1240 °C. Its solidification sequence can be identified as follows: L → γ at 1354 °C; L → γ + MC at 1290 °C; L → γ + Laves at 1120 °C.

Xiaoliang Li, Bo Chen, Weiwei Xing, Long Zhang, Yingche Ma, Kui Liu
##### High Temperature Creep Behavior and Fracture Characteristics of a 2%Ru Nickel Based Single Crystal Superalloy

The creep behavior and fracture characteristics of a new type of 2%Ru nickel base single crystal superalloy was studied through measurement of creep properties and microstructure observation. The results show that the alloy has good creep properties at 1070–1100 °C and 127–147 MPa. The apparent activation energy of creep is: Q = 416.8 kJ/mol and the stress index n is: n = 4.67 at the steady creep stage. The deformation mechanism of alloy in the steady state of creep is that the dislocation slip in the matrix and climb over the γ′ phase in the matrix, and the dislocation can be cut into the γ′ phase in the late stage of creep. Under high temperature and low stress, the γ′ phase of the alloy can form raft structure, and the crack initiation at the interface between the raft γ′ phase and the matrix phase. With the crack propagation, aggregation and connectivity, the creep resistance of the alloy decreases sharply, which eventually leads to creep rupture of the alloy.

Shuang Liang, Sugui Tian, Zhixin Liu, Delong Shu
##### Research and Manufacture of Short-Flow Hot Extrusion Forming and Seamless Pipe for GH3625 Superalloy

In order to obtain GH3625 superalloy seamless pipe, the GH3625 superalloy seamless pipe with Φ28 × 5.5 mm was developed through short-flow hot extrusion forming and cold rolling molding process. And a comprehensive evaluation for the microstructure and mechanical properties of GH3625 superalloy seamless pipe was conducted. The results showed that the hollow tube has been successfully extruded the GH3625 superalloy tube with Φ43 × 9.5 mm under the condition of fixed extrusion speed of 50 mm/s, preheating temperature of 1150 °C and extrusion ration of 7.4. The alloy tube was composed of a small amount of deformation twin and a large number of equiaxed crystal mixed crystal structure, the average grain size was about 8.6, and the tensile strength at room temperature and elongation at break were 771 MPa and 52.33%, respectively, showing good cold working performance and mechanical properties. The performance of GH3625 superalloy seamless pipe after cold rolling and annealing is in accordance with ASTM-B163-04 international standard.

Yubi Gao, Yutian Ding, Bin Meng, Zhengyi Dou, Xin Gao, Zhi Jia
##### Numerical Simulation of Hot Extrusion Process of GH3625 Alloy Tubes

In order to obtain GH3625 superalloy seamless pipe, the GH3625 superalloy seamless pipe with Φ28 × 5.5 mm was developed through short-flow hot extrusion forming and cold rolling molding process. And a comprehensive evaluation to the microstructure and mechanical properties for GH3625 superalloy seamless pipe was conducted. The results show that hollow tube has been successfully extruded the GH3625 superalloy tube with Φ43 × 9.5 mm under the condition of fixed extrusion speed of 50 mm/s, preheating temperature of 1150 °C and extrusion ration of 7.4. The alloy tube is composed of a small amount of deformation twin and a large number of equiaxed crystal mixed crystal structure, the average grain size is about 8.6, and the tensile strength at room temperature and elongation at break are 771 MPa and 52.33%, respectively, and have good cold working performance and mechanical properties. The performance of GH3625 superalloy seamless pipe after cold rolling and annealing is in accordance with ASTM-B163-04 international standard.

Yutian Ding, Bin Meng, Xin Gao, Yubi Gao, Zhengyi Dou, Zhi Jia
##### Hot Deformation Behavior of NiCr19Co6W10Ti3AlB Superalloy

NiCr19Co6W10Ti3AlB alloy is a kind of precipitation hardening nickel-base superalloy, also is a kind of high temperature and high elasticity alloy. The chemical elements of the alloy composition is very complex, it includes more than 4.5% aging strengthening elements of Al and Ti, and nearly 37% solid solution strengthening elements of Cr, W, Co etc. Because of composition segregation in the alloy ingot, the difficulty of hot working is faced. In this paper, the composition segregation and homogenization annealing process of cast NiCr19Co6W10Ti3AlB alloy were studied. The dendrite segregation and its elimination method were investigated by homogenization annealing experiment. High temperature plastic deformation behavior of NiCr19Co6W10Ti3AlB alloy was also studied in this paper. By thermal simulation compression test, the thermal deformation behavior and microstructure change under different deformation conditions were analyzed, which provides a good reference for practical production.

Min Yu, Kaihong Cai, Zhenrui Li, Donghui Xie
##### Hot Forging Behavior of Inconel625 Superalloy Based on Processing Map

The hot forging behavior of Inconel625 superalloys was studied in hot compression tests by the thermal mechanical simulator with Gleeble-3800. The testing conditions were that the maximum strain was 0.8, the deformation temperatures were 950, 1000, 1050, 1100, 1150, 1200 °C, and the strain rates were 0.1, 1, 5, 10, 50, 80/s. The constitutive equation was developed based on true stress (σ)-strain (ε) curves, and the activation energy of Inconel625 superalloy under hot compression was about 679.6 kJ/mol. The processing map was developed based on experiment data and the dynamic material model (DMM), which predicted that the optimum hot working regime of Inconel625 was the compression condition of 1200 °C with 0.1 s−1, and predicted the instability zones were found out under the compression condition of 1100 °C with 0.1 s−1, 1200 °C with 1 s−1, 950 °C with 10 s−1 and 1150 °C with 80 s−1. The microstructure under the compression condition were in good agreement with the predictions of the processing map, under the optimum compression condition of 1200 °C with 0.1 s−1, the dynamically recrystallized grains were finer and the better mechanical properties, this condition should be selected to forging. In contrast, the grain sizes were uneven and the mechanical properties were poorer under the instability compression condition of 1100 °C with 0.1 s−1, 1200 °C with 1 s−1, 950 °C with 10 s−1 and 1150 °C with 80 s−1. Therefore, these instability zones should be avoided during hot forging.

Deshun Sun, Xingzhi Jiang, Jianzhong Shi, Jianhua Huang, Yongzhong Jiang
##### Influence of Composition Adjustment on the Microstructure and Properties of a First Generation Ni-Base Single Crystal Superalloy DD416

The effects of composition adjustment on the microstructures and properties of a first generation Ni-base single crystal superalloy DD416 were investigated. Four experimental alloys with adjusted compositions were directionally solidified and their microstructures were observed with scanning electronic microscope (SEM) and optical microscope (OM). The tensile and creep rupture properties were tested. The results showed that the volumes fraction of eutectic of the as cast alloys and heat treated alloys were obviously influenced by the slightly adjustment of composition, especially the change of Al and Ti contents. The tensile properties of the four experimental alloys were similar, but the creep rupture properties were affected by the adjustment of composition significantly.

Shuai Zheng, Jian Zhang, Qinghui Wu, Zhenyu Yang, Yushi Luo
##### Effect of Hot Isostatic Pressing on the Tensile Property of a Second Generation Single Crystal Superalloy

The hot-isostatic pressing (HIP) process at the condition of 1300 °C/100 MPa, 4 h was applied on the second generation single crystal superalloy DD6. Microstructural evolutions of DD6 alloy after HIP and heat treatment were observed by using optical microscope (OM), scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA). The tensile properties of DD6 alloy after HIP treatment were tested at 760 and 980 °C. The results showed that the volume fraction of porosity in DD6 alloy deceased from 0.31 to 0.04% after the HIP treatment of 1300 °C/100 MPa, 4 h, meanwhile, the dendritic segregation was homogenized gradually. Compared to the standard heat treatment, the HIP treatment did not change the tensile strength and elongation of DD6 alloy at 760 °C obviously. While the elongation of DD6 alloy increased from 24.25 to 35.90% at 980 °C.

Jian Zhang, Huiming Guo, Yunsong Zhao, Yushi Luo
##### Effect of Strain on Recrystallization of a Ni-Based Single Crystal Superalloy

The effect of strain induced by compression testing on recrystallization (RX) of a single crystal superalloy DD6 was investigated. The evolution of surface structure during annealing at the temperatures of 1000, 1100, 1220 °C was characterized by Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS). The element distribution and microstructure of the oxidation layer after annealing at 1100 °C showed that the main chemical elements were mainly Al, Ta, Cr, Ni, O. This indicated that the formation process of oxides included the inward diffusion of O and the outward diffusion of oxide-rich elements (Al, Cr, etc.). The thickness of RX layer was measured. At 1000 °C, no recrystallization but PFZ (precipitate free zone) was observed under oxidation layer. However, when annealing at higher temperature, the thickness of RX layer increased obviously with the increasing deformation strain. Cellular recrystallization could be detected in the samples annealed at 1100 °C, whereas isometric recrystallization and annealing twin formed in the specimen annealed at 1220 °C.

Qian Liu, Lixi Tian, Wenlong Xiao, Chaoli Ma
##### Effect of Aging Treatment on the Microstructure and Properties of K4648 Superalloy

As the superalloy K4648 is a high Cr content alloy, the different heat treatment process affects the precipitation of α-Cr and Cr carbides. In this paper, the heat treatment experiment of K4648 superalloy was carried out. The results showed that the morphology and quantity of α-Cr phase in the alloy were very sensitive to the heat treatment. With the increase of aging temperature, the tensile strength of the alloy at room temperature decreased gradually, and the elongation and contraction furnace gradually increased, and the room temperature impact toughness increased to a certain extent and remained unchanged.

Yang Gao, Yongji Niu, Zhenrui Li, Rong Zhang
##### Precipitation Behaviors of M23C6 Carbides and γʹ Phase in Cast IN617B Alloy During Long-Term Aging

The precipitation behaviors of M23C6 carbides and γʹ phase in cast IN617B alloy during long-term aging was systematically investigated by comparison with previous studying results about wrought IN617B alloy. The results showed that the morphology of M23C6 carbides and the nucleation location of γʹ particles in cast IN617B alloy were distinctly different from those of wrought IN617B alloy due to the difference of processing method. The microstructure observation revealed that the morphology of M23C6 carbides at grain boundaries (GBs) transformed from film-like shape into cellular shape owing to the reduction in the interfacial energy of GBs. Within the grains the bar-like M23C6 carbides and spherical γʹ phase directly precipitated from the γ matrix. Moreover, the growth of M23C6 facilitated the formation of γʹ phase by enriching γʹ-formation elements, and conversely, dense γʹ phase inhibited the coarsening and decomposition of M23C6 by constraining the diffusion of M23C6-formation elements. In addition, the mechanism of inhibiting effect of γʹ phase on the coarsening of bar-shaped M23C6 was discussed.

Shuang Gao, Jieshan Hou, Fei Yang, Changshuai Wang, Lanzhang Zhou
##### Effect of Aluminum on Microstructure, Mechanical Properties and Castability of a Directionally Solidified Superalloy

The effect of aluminum (Al) on microstructure, mechanical properties, solidification behavior, segregation and castability of a directionally solidified Ni-based superalloy was investigated. It was found that the dendrite arm spacing and volume fraction of carbides slightly decreased, while the volume fraction of the γ/γ′ eutectic decreased distinctly with the decrease of Al content. When Al content reduced, the tensile properties at room temperature slightly decreased while the stress rupture life reduced significantly at 980 °C/235 MPa. The change of liquid volume fraction slightly reduced while the residual liquids were more inclined to remain thin continuous network form during the solidification in the alloy with low Al content. The segregation degree of Cr, Mo and W decreased with decreasing Al content, while Co, Al and Ta were more likely to segregate towards the interdendritic regions in the alloy with low Al content. The castability of alloy was getting worse with decreasing Al content.

Zheng Tan, Jian Tong, Wenshu Tang, Likui Ning, Enze Liu, Zhi Zheng, Yichuan Liu
##### Effect of Solution Treatment on Microstructure and Mechanical Properties of HGH163 Alloy

Ni-based superalloy HGH163 wire was studied in this paper. The microstructure and properties of HGH163 wire subjected to different solution treatments were investigated by the mechanical properties testing, metallographic microscope and scanning electron microscope analysis. The results show that the solid solution temperature significantly affects the microstructure and mechanical properties of HGH163 alloy. With the increase of heat treatment temperature, the tensile strength decreased, the plastic deformation of grains increased significantly, changing from the deformed grain to equiaxed ones.

Huiyun Wu, Qingquan Zhang, Chao Wang, Bing Wu, Ran Wei, Yu Cao
##### As-Cast Microstructure and Mechanical Properties of a New Superalloy

In this paper, we have investigated the as-cast microstructure, mechanical properties and alloying elements of Ni-11.5Cr-3.0Mo-2.0Al-1.0Nb-0.4Ti-0.05C alloy. The results indicated that the microstructure of the alloy are mainly composed by γ phase, γ′ phase and carbides. With increasing temperature to 760 °C, the strength and plasticity of the alloy decreased obviously. In addition, as the contents of alloying elements in the alloy like Al, Mo, Nb and Ti are increased, the microstructure of the alloy don’t change obviously, but a increase of tensile strength is obtained at room temperature and the plasticity decreased about 0.5%.

Zhiwei Zhang, Yongji Niu, LiZhe Rui
##### Weld Properties of Haynes214 Alloy

Haynes214 alloy should be welded together with other alloys when it is used as brush seal materials. In the present investigation the welding performance of Haynes214 alloy welded with GH4169 alloy and GH625 alloy was carried out. The microstructure and mechanical properties of the welding joint under different conditions were studied. The results showed that no liquation crack or other defect existed at the welding joint of Haynes214-GH4169 and Haynes214-GH625. After aging, the room temperature tensile strength of Haynes214-GH4169 and Haynes214-GH625 welding joints was approximately 94% of Haynes214 alloy. The high temperature (500 °C) tensile strength of Haynes214-GH4169 welding joint was about 85% of Haynes214 alloy, while Haynes214-GH625 welding joint was about 75% after aging.

Ran Wei, Qingquan Zhang, Huiyun Wu, Chao Wang, Yu Cao
##### Tensile Properties and Phase Precipitation of K423A Alloy at High Temperature

In this paper, K423A alloy was subjected to high temperature tensile test using a metal material universal testing machine. The microstructure of the alloy was observed by scanning electron microscopy. The precipitation phase of the alloy was analyzed by phase diagram calculation software and XRD analysis. The results show that the tensile strength and yield strength of the alloy decrease with the increase of temperature in the range of 700–950 °C. The elongation increases first and then decreases, and the highest value occurs at 900 °C. The main strengthening phase of the alloy is found to be γ′ phase, and MC, M6C, M23C6, μ phase, σ phase and boride are precipitated during the solidification process.

Jianjun Tian, Zhenrui Li, Yongji Niu, Zhiwei Zhang, Yang Gao
##### Metallurgical Controlling of La in a Superalloy

In this paper, the burning law of La in VIM + ESR double-smelting-processing was studied in an alloy containing La. The results showed that the added La was almost burn out when added in after the refining in a vacuum induction melting process. However, when La was added at the end of smelting and before tapping, La can be effectively preserved. The burning rules of electroslag remelting slag system of CaF2:Al2O3, CaF2:Al2O3:CaO and CaF2:Al2O3:CaO:La2O3 was examined, and the results showed that the recovery rate of the first two slag series La was between 13 and 19%, and the burning loss of the two slag series La was not very different. The recovery rate of La in the slag system with La2O3 was 10–13%, the loss of La was significantly over the previous two large slag systems. But in terms of the La uniform in different parts of alloy ingot the slag containing La2O3 was the best.

Yong-ji Niu, Hai-wen Liu, Zhi-wei Zhang, Ning An, Yang Gao, Jian-jun Tian
##### High Temperature Oxidation of Superalloys in Steam Environment

High temperature oxidation of superalloys in steam environment was studied. The experimental results showed that the oxidation resistance of the superalloys in steam environment was superior to heat resistant steel HR3C. Only the oxide scale formed on Super 304H steel was spalled at 800 °C. The oxide scales formed on superalloys Haynes 282 were composed of an external oxide layer of TiO2 and Cr2O3 and an internal oxide layer of Al2O3, TiO2 and Cr2O3. A uniform MnCr2O4 and Cr2O3 formed at the surface of superalloys Haynes 120 and Haynes 625. It was concluded that Cr and Ni improved the oxidation resistance in steam environment. The penetration depth of internal oxides was decided by the contents of Al and Ti. Finally, the oxidation resistance index of superalloys was comprehensively evaluated by the weight gain, oxide scale thickness and Cr depletion depth.

Zhiyuan Liang, Miao Yu, Yong Gui, Preet Singh, Qinxin Zhao
##### Effect of LMC Processing Parameters on Casting Defects in Large-Scale Single Crystal IGT Blades

The effects of liquid metal cooling (LMC) processing parameters including mold shell temperature, withdrawal rate and metal pouring temperature on casting defects of large-scale single crystal blades were investigated by orthogonal experiments. The results of range analysis showed that with the withdrawal rate increasing from 5 to 8 mm/min, primary dendrite arm spacing (PDAS) and secondary dendrite arm spacing (SDAS) were refined obviously. But the number of casting defects especially stray grains (SG) in transition region and helical section increased, because the solid-liquid interface became more concave. With the pouring temperature increasing from 1550 to 1570 °C, the number of casting defects increased. Dendrite structure was refined slightly and the solid-liquid interface became less concave with the mold shell temperature increased from 1540 to 1560 °C. Finally, the suggestions were proposed to optimize the LMC processing parameters and control casting defects formed during directional solidification.

Wenjin Wu, Jingyang Chen, Qing Li, Lin Liu, Lamei Cao, Xin Tang, Chengbo Xiao
##### Formation Mechanism of Oxide Scales Grown on X10CrAlSi18 and 310S Heat-Resistant Stainless Steels Under High Temperature in Air

To promote the application of resource-saving heat-resistant stainless steels, the study on high temperature oxidation behavior and oxide-scales formation mechanism of X10CrAlSi18 ferritic heat-resistant stainless steels (FHSSs) and 310S austenitic heat-resistant stainless steels (AHSSs) was carried out in air up to 140 h, and the microstructure of oxide scales, oxidation kinetics and thermodynamics theories, and the classical hypothesis of the third-element effect analyzed. The results showed that the cost-effective X10CrAlSi18 FHSSs presented good oxidation resistance at 800 and 900 °C due to the compact multicomponent oxide scales composed of Al2O3, Cr2O3, MnCr2O4 and MnFe2O4 and good adhesion to the matrix. However, the oxidation resistance of the alloy at 1000 °C was deteriorated, which is mainly due to the non-protective Fe2O3. The oxide scales of 310S AHSSs containing Cr2O3, MnCr2O4 and inner SiO2 exhibited good oxidation resistance, while the internal oxidation of silicon weakened the adhesion to the substrate.

Yuqing Zhou, Dening Zou, Wei Zhang, Yingbo Zhang, Lei Du
##### Heat Treatment of a New Designed Ni-Based Single Crystal Superalloy

The heat treatment for a new designed Ni-based single crystal superalloy was investigated. The solution heat treatment was confirmed as 1260 °C/2 h + 1280 °C/4 h, AC through differential scanning calorimetry (DSC) curves and incipient melting experiments. The aging heat treatment was determined as 1120 °C/4 h, AC + 870 °C/32 h, AC according to the high temperature stress rupture tests for samples aging at different temperatures. Results showed that the eutectic was completely dissolved after solution heat treatment. The γ′ phase was uniformed in suitable size after aging heat treatment. The stress rupture test at 1070 °C/140 MPa showed the rupture life of alloy after heat treatment was 163.25 h. The segregation degree of alloying elements after heat treatment was decreased obviously.

Yichuan Liu, Zheng Tan, Wenshu Tang, Zhi Zheng, Enze Liu, Jian Tong, Likui Ning
##### Effect of Oxygen Content of Powders on Previous Particle Boundaries in Hot Isostatic Pressed TiAl Alloy

Argon gas atomized Ti–43Al–9V–0.3Y alloy powders with oxygen contents of 1150 and 550 ppm respectively were hot isostatic pressed (HIPed) at 1200 °C and 150 MPa for 3 h to obtain full density compacts. The effect of powders oxygen content on previous particle boundaries (PPBs) was investigated. Results show that PPBs only were observed in the HIPed compact produced from the powders with 1150 ppm oxygen content, and higher oxygen content promoted the formation of PPBs in TiAl alloy. SEM and TEM analysis proved that the microstructure at PPBs was α2/γ lamellar. Oxygen was the α2 phase stabilizer, and it restricted the α → γ transformation but drived the α → α2 + γ eutectoid process in which the lamellar formed.

Yufeng Liu, Zhou Li, Na Liu, Liang Zheng, Wenyong Xu
##### Effect of Solution Treatment on Microstructure and Properties of GH3625 Alloy Tubes in Different States

The influence of solution treatment temperature on microstructure evolution and mechanical properties of the GH3625 alloy tubes in different states (hot extrusion, cold rolled and annealed) were investigated by organization characterization(OM, SEM) and performance tests (hardness test and tensile test at room temperature). The results showed that the mixed grain structure of the hot extruded GH3625 alloy degraded and transformed into uniform equiaxed grain structure, as the solution treatment temperature was 1000 °C. When the solution temperature was higher than 1050 °C, the microstructure of the cold rolling GH3625 alloy was uniform equiaxed grain, and the solution amount of the carbides increases with the increase of the solution temperature. The microstructure of annealed GH3625 alloy in the whole solution temperature range (950–1150 °C) was fully recrystallized equiaxed grain, and there were a large number of lath-shaped annealed twins in the grains. The microstructure and mechanical properties of the GH3625 alloy during the solution treatment were not only affected by the solution temperature, but also influenced by the original states. After solid solution treatment at 1150 °C for 60 min and then water-cooling, the tensile fracture modes of GH3625 alloy tubes under different conditions was ductile fracture. The temperature of 1150 °C can be used as the reference temperature for optimizing the microstructure and properties of GH3625 alloy through solution treatment in different states.

Yutian Ding, Bin Meng, Yubi Gao, Yuanjun Ma, Jianjun Chen
##### Effects of Ce and Dy on the Cyclic Oxidation Behavior of a Ni-Based Single Crystal Superalloy

To understand the role of rare earth elements in influencing high-temperature oxidation behavior of the Ni-based single crystal superalloy, a high Mo-containing nickel-based single crystal superalloy and the derivative alloy modified by Ce and Dy were designed. The results of oxidation tests conducted at 1100 °C indicated that doping 0.022 wt% Ce or 0.042 wt% Dy significantly improved the oxidation resistance of the alloy by reducing the oxide scale growth rate and enhancing the scale adhesion. The positive effects are probably because the doped trace of Dy or Ce can combine with O2− more quickly and reduce the oxygen contents on the oxide surface which decreases the oxidation rate. At the same time, it decreases the thickness of oxide scale which results in the reduction of the elastic strain energy and the weaker tendency to spallation of the oxide scale. But too high concentration of Dy or Ce was deleterious because its high oxidation rate results in much more defects which induce cracks easily.

Jieying Bai, Jianhao Wu, Shuhua Xu, Yanling Pei, Lu Qin, Shusuo Li, Shengkai Gong
##### Tensile Fracture Characteristics Along Different Directions of Laminated Ti-TiBw/Ti Composites with Two-Scale Hierarchical Structures Fabricated by Reaction Hot Pressing

The tensile behaviors and fracture characteristics of laminated Ti-TiBw/Ti composites with two-scale hierarchical structures along different directions were investigated in detail. The laminated Ti-TiBw/Ti composites exhibited the highest tensile strength and fracture elongation along the longitudinal direction. Multi-necking and interfacial “intercrystalline-like” network fracture dominated the fracture behaviors along the transversal direction, which are attributed to the high strain ( $$\mathop \varepsilon \nolimits_{\text{Ti}}$$ ), low strain hardening exponent ( $$\mathop n\nolimits_{\text{Ti}}$$ ) of Ti layer, and obvious strain misfit at the interface, respectively. The longitudinal fracture characteristics of laminated Ti-TiBw/Ti composites reveals diffuse necking delaying, localized shear band transferring, tunnel cracks blunting, micro-cracks insensitivity, crack bifurcation and interfacial delamination absenting phenomena, which are beneficial to the toughening the laminated composites.

Baoxi Liu, Lujun Huang, Xiping Cui, Lin Geng, Fuxing Yin
##### Enhanced Mechanical Properties of Al7075 Alloy with Graphene Nanoplates Prepared by Ball Milling and Hot Extrusion

In this study, Graphene Nanoplates/Al7075 (GNPs/Al7075) composites were prepared by powder metallurgy and hot extrusion. And the microstructure and mechanical behavior of GNPs/Al7075 composites prepared by ball-milling and hot extrusion were investigated. Compared with the unreinforced Al7075 matrix, these composites possess significantly improved stiffness and tensile strength.

Teng Wang, Yitan Zhang, Guodong Li, Chaoli Ma, Wenlong Xiao
##### Microstructure and Thermal Properties of SiC/Al Composites for Electronic Packaging

The SiC particles reinforced aluminum matrix composites for electronic packaging was prepared by using pressureless infiltration. The microstructures and thermal properties were investigated. The results shown that the composites were free of porosity, the SiC particles were distributed uniformly and which interfaces were well controlled. The bending strength was less affected by different loading speeds, the experimental results shown that the average bending strength was more than 360 MPa. By studying the fracture surface of bending specimens, the SiC particles were brittle cleavage fracture and the matrix was ductile tough fracture. The thermal performance test results indicated that the coefficient of linear expansion increased first and then decreasing with the temperature rising, and the maximum value is 8.25 × 10−6 K−1 near 300 °C. The thermal conductivity decreased gradually, when the temperature is 25 °C, the maximum thermal conductivity was 225.7 W m−1 K−1, and the density was 2.95 g/cm3, meet the requirements of electronic packaging materials.

Tong Lu, Yan Wang, Qiang Yao, Qiong Wang, Yu Hong Zhu
##### Analysis of Uniformly Distributed Limit Load for Circular Plate by TSS Criterion

In order to analyze the uniformly distributed limit load for circular plate, a trial function of deflection with cosine form is investigated by the variational method. With the specific plastic work of the Twin Sheer Stress (called TSS for short) criterion, the internal deformation power is deduced. ATn analytical solution of limit load based on the TSS criterion is obtained as a function of circular plate radius a, thickness h and yield stress $$\sigma_{s}$$ . Compared with the available solutions based on Tresca and Mises criteria, it is shown that the present result is the highest, but the relative error between the present one and the Mises result is only 0.77%. The deflection increases with the decrease of plate thickness or the increase of the ratio of r/a, and the limit load decreases with the increase of plate radius.

Siwei Gao, Shunhu Zhang, Guijing Wu, Jian Cao
##### Interfacial Diffusion Behavior of Thermal Bimetal 5J20110 with High Sensitivity

The thermal bimetal 5J20110 with high sensitivity was prepared by cold rolling bonding process, the effect of diffusion annealing temperature and time on the properties and interfacial diffusion behavior of 5J20110 was studied. Combining with the principle of diffusion, the diffusion law of interfacial alloy elements was calculated and analyzed, and the relation that the interfacial diffusion layer thickness varying with diffusion annealing temperature and time was deduced. The results showed that the diffusion trend of alloy elements enhanced gradually and the thickness of diffusion layer increased gradually with the increase of diffusion annealing temperature and time, and the bonding strength and resistivity of the thermal bimetal varied little. It is found that the interfacial diffusion layer is solid solution, and the diffusion layer thickness is proportional to the square root of diffusion time t1/2 and e−1/T of diffusion temperature T. The formula for the growth of the interfacial diffusion layer thickness derived in this paper can provide the basis for optimizing the diffusion annealing process.

Donghui Xie, Jing Zhang, Zhi Qin, Min Yu, Weifeng Peng
##### Effect of Intermediate Annealing on the Interface and Plasticity of Cu–Ni–Si/Al–Mg–Si Clad Composite Wires

The aim of this article is to study the effect of intermediate annealing on the interface and plasticity of Cu–Ni–Si/Al–Mg–Si clad composite wires. Cu–Ni–Si/Al–Mg–Si clad composite wires were produced by cold drawing process and annealed at the temperature from 150 to 350 °C for 0.5 h. The presence of various intermetallic compounds in different temperature was detected by scanning electron microscope and EDS analyzer. The mechanical properties were measured by stretch test. The elongation increased with the temperature increment. The morphology of fracture showed that intermetallic compounds were tough and brittle. During the subsequent drawing, the intermetallic compounds were harmful to the overall structure of composite wires. The elongation cannot identify the plasticity of copper-clad aluminum (CCA) composite wires accurately.

Zhen Yang, Xujun Mi, Haofeng Xie, Lijun Peng, Guojie Huang, Xue Feng, Xiangqian Yin
##### Thermodynamics and Morphological Fractal Characteristics of WC Particulates Reinforced Steel Matrix Composites by Composite Electroslag Melting and Casting

The composite electroslag melting and casting technology was adopted to produce 45 wt% WC particulate reinforced steel matrix composites. The results indicated that the WC formation showed a dominant position and displays in a triangle or rectangle in the WC reinforced steel matrix composites. As a reference plane, WC grains in the $$(0001)$$ surface grew up into a stack structure in the way of hierarchical formation along the $$\left\langle {0001} \right\rangle$$ direction, finally formed a three-dimensional shape with the $$(0001)$$ surface in a triangle. The fractal dimensions of WC present different changed with the transformation of the heat treatment process. When quenched and tempered at high temperature, the fractal dimension value of two types of WC appeared, and WC phases showed two groups of different fractal structure with different particle size and quantity. The larger fractal dimension difference $$\Delta D$$ corresponded to Fe3W3C compound carbides, with the smaller $$\Delta D$$ to WC particles which keeps the properties and morphology under the state of forging and annealing. The higher the quenching or tempering temperature, the larger the fractal dimension difference $$\Delta D$$ and the greater change of the morphology of WC were obtained.

Ning Zhang, Chunhong Zhang, Mingfan Zhu, Yinghuai Qiang
##### Effect of TiB2 Content on Wear Resistance of TiB2/7055 Composite Materials

TiB2/7055 composites with volume fractions of 0, 5.17 and 18.23% were prepared by two step method. Firstly, the Al/TiB2 master alloy was prepared by Melt Self-propagating High-temperature Synthesis method. Then, TiB2/7055 composite was prepared by adjusting the alloy elements with using this master alloy as the matrix. Meanwhile, the effect of TiB2 particle content on hardness and wear resistance of the composites were studied. The microstructure of the composite was observed by SEM and TEM. The result showed that the average size of TiB2 reinforced particles were less than 1 μm and the particles were dispersively distributed in the grain. With the increasing of the TiB2 particles content, the hardness and wear resistance of composites increased. When the volume fraction of TiB2 was 18.23%, the hardness of composite after T6 aging could reach to 264HB, which is 14.29% higher than 7055 alloy (T6 aging), and the wear resistance is 32.36% higher than that of the 7055 alloy.

Haijing Wang, He Li, Lihua Chai, Tiejun Ma, Ningning Jian, Tounan Jin, Ziyong Chen, Guodong Shi
##### Effect of Graphite Content on the Tribological Properties of Cu–Graphite–SiO2 Composites

Cu–graphite–SiO2 composites with different graphite content were fabricated by vacuum hot-pressing sintering. Pin-on-disk friction and wear tester was used to carry out the friction test and study the tribological behaviors of Cu–graphite composites. The results show that the fabricated composites had good compactness and the relative density reached 96.2%. With increasing graphite content, the density, hardness and electric conductivity of composites all declined. The friction coefficient and wear rate both declined at first and then increased and obtained the lowest value (0.198 and 1.062 mg/m, respectively) at 15% graphite. The composite with 15% graphite showed the best tribological properties. The wear mechanism of composites with lower graphite content is mainly abrasive wear. The wear mechanism of the composite with 15% graphite is plastic deformation. When graphite content increased to 20%, fatigue wear and delamination turned into the wear mechanism of the composite.

Yifei Ye, Xu Ran, Bozhe Dong, Yanyi Yang
##### Design and Numerical Simulation of a Novel Mixer in Preparing SiCp/A357 Composites

Aim at uniform SiCp-particle distribution in aluminum matrix composite, a novel mixer for preparing SiCp/A357 composites was designed, and a flow model based on standard κ-ε model was developed to simulate the flow behavior of the SiCp/A357 composites stirred by the novel mixer, at last the structural parameters of the mixer were optimized and verified by numerical simulation and stir casting experiment. The results showed that the appropriate mixer parameters were as following: the diameter was 150 mm, the layer spacing was 40 mm and the gap distance to the crucible was 40 mm. The SiCp particles distributed uniformly in the aluminum matrix and the stir casting experiment results were in accord with the numerical simulation, the mixer was effective to produce the high-quality SiCp/A357 composites.

Yuelong Bai, Zhenlin Zhang, Zhifeng Zhang, Chunsheng Chen, Jun Xu
##### Effect of EPS Porogen on Microstructure and Properties of ZTAp/High Chromium Cast Iron Composites

The expandable polystyrene was added to the gap in the ceramic preform which was made of ZrO2 toughened Al2O3 (ZTA) ceramic particles. Increasing the porosity of the preform is beneficial to the high chromium cast iron infiltration and can obtain the composites of ZTA particles reinforced high chromium cast iron matrix. In this paper, studied the residues amount of the different porogen in the preform such as 10 ~ 20 mesh, 20 ~ 40 mesh, 40 ~ 80 mesh, 80 ~ 120 mesh and mixing particle sizes were heated to the temperature of 250, 350, 450, 550 °C. The corresponding composites were obtained under the different conditions and the interfacial effect, the wear resistance of the composites were observed. At the same time, the fracture mode of the composites was analyzed. The results showed that the porosity of preform with mixing particle sizes was the lowest at 550 °C and had the best interfacial, the highest wear resistance. The fracture mode of the composites was the particles fracture, metal matrix brittle fracture and the particles shedding from the matrix.

Mojin Zhou, Yehua Jiang, Xiaozu Zhang, Nan Wang
##### Preparation and Characterization of Electroless Copper Coating on Hollow Glass Microspheres

The electroless copper coating was prepared on the hollow glass microspheres. To reduce the cost, the silver nitrate activator was used instead of conventional PdCl2. The coated microspheres were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffractometry (XRD). The continuous and uniform Cu coating was obtained on the microspheres under the optimized electroless process and the thickness of Cu coating was identified to be about 100 nm. The silver nitrate activator has been demonstrated to be effective replacement for the PdCl2 activator.

Dan Liu, Qiang Zhang
##### Anti-irradiation Performance of Al–Si–Zn–O Compound Coating on Kapton/Al Second Surface Mirror

An Al–Si–Zn–O compound film was prepared on the surface of Kapton/Al second surface mirror by hydrothermal growth and sol-gel methods. The microstructure, composition, optical and thermal performances of the coatings before and after irradiation were investigated compared to the unprotected surfaces. It was shown that the compound coating had a structure of AZO particles coated by continuously distributed amorphous SiO2 and displayed denser and smoother. With this compound coating the resistivity of Kapton/Al second surface mirror to space proton and electron radiation was greatly improved, while the optical and thermal performances of the protective coating degraded much less than that of the unprotected coating.

Gang Liu, Huifen Wang, Yujing Li, Bo Zhou, Yangyang Pan
##### Depth Distribution of High Energy Proton in Polyimide Film

In order to study the process of high energy proton passing through a thin film, a non-equilibrium statistical model of proton irradiation was established on the basis of stochastic theory. Considering the statistical model and the electronic stopping power, the Langevin equation and the corresponding Fokker–Planck equation were given, then the average passing depth and the changes of probability density distribution of passing depth with energy or time were calculated. By analysis, the average passing depth of the high energy proton in the film was calculated. The probability density distribution of the passing depth represents the probability that protons pass to a certain depth.

Bin Rong Wang, Yan Hua You, Hai Yun Hu
##### Research on Properties of Refractory Metal and Composites

Three refractory metal composites were prepared by powder metallurgy, that is. W–7Cu, Mo–10Cu and W–26Re. Properties of the materials were studied, such as tensile strength, fracture toughness, elastic modulus and ablation resistance. The results show that W–26Re has the best mechanical properties and ablation resistance. The tensile strength is 350 MPa at 1600 °C. And the linear ablative ratio is 3.37%, and the linear ablative rate is 0.006 mm/s at 2500 K of ablation of 600 s. It has wide potential application in the high-temperature working environment.

Baohong Zhang, Di Dong, Chengyang Wang, Danhua Zhang
##### Investigation of High-Temperature Mechanical Property and Fracture Mechanism of Tungsten Alloy

In this study, 93W–5Ni–2Fe tungsten heavy alloy prepared by powder metallurgy method were tested at 1000, 1100, 1200, 1300 and 1400 °C respectively for investigating high temperature mechanical properties. Fracture analysis was carried out by scanning electron microscope and then developing principles of fracture mechanism obtained. The results showed that as the elevating temperature in the range of 1000–1400 °C, mechanical properties of 93W–5Ni–2Fe alloy, such as tensile strength, elongation, reduction of area and Young’s module were dramatically getting worse. Material becoming brittle, transgranular fracture hardly found, binder phase tear and interfacial fracture between tungsten grain and binder phases are domestic fracture mode.

Guohui Liu, Ling Wang, Yingnan Qin, Guirong Liu, Ning Xiong
##### Effects of Ce Addition on Mechanical Properties and Microstructures of Mo Alloy Wires

The effects of Ce addition on mechanical properties and microstructures of Mo–Ce alloy wires were investigated. The results show that the yield strength (Rp), tensile strength (Rm) and elongation to failure (A%) of Mo–Ce alloy wires were sensitive to the Ce content. When the Ce content was less than 0.03 wt%, Rp, Rm and A% did not change significantly as comparing with the unalloyed molybdenum wires; when the Ce content was ranging from 0.06 to 0.09 wt%, Rp and Rm gradually increased, and the decreasing of A% was accompanied; when the Ce content was ranging from 0.09 to 0.12 wt%, the maximum A% and moderate Rp and Rm were obtained; when the Ce content was ranging from 0.15 to 0.3 wt%, Rp, Rm and A% decreased simultaneously. The optical microstructures of as-sintered Mo–Ce alloys show that the grain sizes of Mo–Ce alloys were 20–30 μm, which were almost equivalent to one quarter of those of unalloyed molybdenum. In addition, the TEM and XRD analyses show that Ce element homogeneously dispersed in the intra- and inter-granular molybdenum substrate in the form of CeO2 particles during the whole preparation processing. Due to that the lattices of CeO2 particles were partly coherent with the molybdenum matrix, they not only had the significant grain refinement and dispersion strengthening effects, but also served to inhibit the brittle-to-ductile transition behaviors of Mo alloys during the subsequent thermo-mechanical procedure. Therefore, the comprehensive mechanical properties of Mo–Ce alloys are much superior to those of the other oxide-dispersion-strengthened molybdenum alloys.

Pengfa Feng, Xiaoming Dang, Na Wang, Qinli Yang, Weicheng Cao
##### Constitutive Model for Molybdenum-Niobium Alloy During Hot Deformation

Isothermal compression of the molybdenum-niobium alloy was conducted on a Gleeble-3800 thermal simulator at the deformation temperature range of 1100–1300 °C with strain rates ranging from 0.001 to 10 s−1 and height reduction of 50%. The results show that the deformation temperature and strain rate affected the flow stress during the thermal deformation of molybdenum-niobium alloy significantly. The true stress–strain curves exhibit a peak flow stress, flow softening and steady flow behavior. The activation energy ( $$Q$$ ) and stress exponent ( $$n$$ ) of molybdenum-niobium alloy, are calculated. The constitutive equation is established based on a hyperbolic-sine equations of Arrhenius type.

Wen Zhang, Xuanqiao Gao, Jun Cheng, Laiping Li, Zhongwu Hu, Bin Zhao, Pingxiang Zhang
##### Diffusion Bonding Properties of Large Dimension WTi Alloy Target Bonded to the Back Plate

In this paper, large dimension WTi alloy target for 12 in. wafers was respectively diffusion bonded to Al alloy, Cu alloy or Mo back plate. Then the properties test of the overall deformation after bonding, interface microstructure, bonding rate, tensile strength were conducted. The results showed that after the large dimension WTi alloy target bonded to the Al alloy or Cu alloy back plate, the overall deformation was large, the target was easily crack or debonding, so the reliability was poor. After the WTi alloy target bonded to the Mo back plate, the overall deformation was small, the bonding rate could reach more than 99%, and the tensile strength could be more than 50 MPa which was better than the traditional solder bonding strength (<5 MPa) and could meet the high power sputtering.

Zhaochong Ding, Haiyang Yu, Xiaoyong Wan, Ming Chen, Yongming Wang, Jifeng Lei
##### W–Cu Tube Processing and Structure Property by Powder Extrusion Molding

In this paper, W–30%Cu tube with 0.8 mm inner diameter, 8 mm external diameter and more than 200 mm on length was shaped using powder extrusion molding and infiltration sintering process. The results showed that the parameters such as powder loading, hot degreasing temperature and sintering temperature and time affected the formability and structure property of W–Cu tube. High properties of W–30%Cu tube with a relative density of 99.6% and an electric conductivity of 49%IACS were obtained when sintering at 1300 °C for 2 h and the powder loading was up to 60%. The effects of sintering temperature and time on the macro-structure and micro-structure were studied.

Shengli Han, Liqun Cui, Daren Li
##### Sintering Fabrication and Characterizations of Powder Metallurgy Targets for Integrated Circuits

Many refractory metal and alloy films are used in Integrate Circuits processing for varied applications, such as plug, barrier layer, glue layer, gate layer, bond-pad, and etc. Usually these films are deposited from powder metallurgy (PM) targets including tungsten, tungsten titanium alloy, molybdenum, silicide alloy, chromium, ruthenium, and etc. On one hand, sintering fabrication methods for these targets, such as atmospheric pressure sintering, Hot Pressing (HP), Hot Isostatic Pressing (HIP) and Spark Plasma Sintering (SPS), are presented in this paper. And the influence of sintering methods on the target’s performance is also discussed. On another hand, the characterizations of powder metallurgy targets are also discussed, such as purity, density, grain size, grain orientation, and uniformity.

Zhaochong Ding, Xiao Liu, Yonghui Wang, Zhuang Wang, Qiankun Xia, Yongjun Li
##### Sintering of Nano Molybdenum Powder

Molybdenum is a rare refractory metal with low thermal expansion coefficient, good thermal and electrical conductivity, high modulus of elasticity. However, the plasticity and processing properties of molybdenum restrict its application in the field of high technology. In the present paper the sintering process mainly by conventional sintering based on the nano molybdenum powders was studied, the effects of powder size, sintering temperature and soaking time on the density, microstructure, mechanical and physical properties of molybdenum products analysed. The experimental results show that nano Mo powder compact had a lower temperature to densification compared with micron-powder compact. It is suggested that 1550 °C is the most appropriate temperature to obtain the best mechanical and physical properties.

Bohua Duan, Zhao Zhang, Dezhi Wang
##### Migration of Liquid Phase in Dual-Layer WC-9Ni Cemented Carbides

The liquid phase migration (LPM) in the sintering process of WC-9Ni dual-layer cemented carbides and its mechanism were investigated and discussed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) system. Moreover, the effect of sintering temperature and WC grain size on micro-structure changes of the samples was also studied. The results indicated that the LPM of dual-layer cemented carbide at different stages in the sintering process was mainly dominated by capillary force, the decrease of inter-facial energy in fine WC layer (FWC layer) and Ni content concentration gradient in the coarse WC layer (CWC layer). During the sintering process, liquid phase first migrated from FWC layer to CWC layer due to the effect of capillary force. With the temperature increase, the liquid phase in turn flowed from CWC layer to FWC layer resulted from the decrease of inter-facial energy of FWC layer. A high temperature sintering (1450 °C) might lead to the formation of an abnormal WC grain growth layer (AWC layer) with relative high Ni content and many pool defects in the CWC layer next to the interface. With the increase of WC particle size in the CWC layer, the quantity of the pool defects in the CWC layer near the interface increased, so did the size.

Kaihua Shi, Xiuqi Zan, Liao Jun
##### Research on the Mechanical Behaviors of TZM Alloys at Room and Elevated Temperatures Prepared for Isothermal Forging Die

TZM alloys used as isothermal forging die at high temperature were prepared by a new powder doping process combined with the rational design of sintering technique and hot working technology. In this paper, tensile properties of TZM alloys at room temperature and properties such as tensile properties, fracture toughness and stress rupture at elevated temperatures were investigated. The results show that the mechanical properties at room temperature were excellent in accord with the ASTM B386-03 (2011) standard. At the temperature of 1100 °C, the tensile and yield strength were 552 and 514 Mpa respectively, and the endurance life is 250 h under the load stress of 160 Mpa, the TZM alloys can be used as isothermal forging die material at temperature of 1100 °C or above.

Jingbo Fu, Weicheng Cao, Geng An, Qinli Yang, Fei Zhuang, Xiao Zhang, Pengfa Feng, Chunyang Bo
##### Study on Rolling Process of Doped Tungsten Sheets

The evolution of density of tungsten sheets with different dopant content is studied. The microstructure evolution and annealing behavior of three kinds of tungsten sheets with deformation of 63, 83, 92%, are studied. The results show that when rolling deformation reaches to 92%, the density of lanthanum-doped tungsten sheets increases from 18.4 to 18.9 g/cm3, and the density of Potassium-doped tungsten sheets increases from 17.6 to 19.15 g/cm3. The deformation of lanthanum oxide particles increases with the increment of deformation, and the tungsten sheets exhibit a typical rolling state. The microstructure of doped tungsten sheets at high temperature is more stable than that of the pure tungsten ones.

Mei Gui Qi, Ai Long Zheng, Rong Kui Fan, Zhi Min Huang, Fu Sheng Peng, Yong Hua Xie
##### Effect of Nd-Doping on the Microstructure and Magnetic Properties of NdX(Fe47.5Pd52.5)100-X Films

In order to investigate the effect of rare earth Nd doping on FePd alloy thin films, the samples of Ndx(Fe47.5Pd52.5)100-x (x = 0, 2, 2.7, 3.4, 4) films were prepared by a DC magnetic sputtering method. The microstructure and magnetic properties were characterized by XRD, EDS, PPMS et al. The XRD data indicated that the addition of rare earth element Nd could significantly shorten the annealing time and the annealing temperature from the disordered FCC phase to the ordered FCT phase and increase the driving force of the phase transition. In addition, the appropriate addition of Nd element also has the role of grain refinement. The grain size could reach 29–14 nm and the appropriate grain size was conducive to the exchange coupling between the grains. The hysteresis loop of the films showed that the coercivity (Hc) and remanence ratio (Mr/Ms) first increased with the increase of Nd content sharply and then decreased. When the content of rare earth x = 2.7, the maximum coercivity was 3.05 kOe. The changes of coercivity and remanence ratio with the increase of annealing temperature also first increased and then decreased, and reached the maximum at 550 °C.

Jianjun Huo, Gang Cheng, Yusong Du, Kuang Pan, Lin Li
##### Erratum to: Microstructural Evolution During Homogenization Heat Treatment for an Al–0.92Mg–0.78Si–0.60Zn–0.20Cu–0.12Zr Alloy

Homogenization heat treatment on an Al–0.92Mg–0.78Si–0.60Zn–0.20Cu–0.12Zr alloy was investigated by OM (optical microscopy), DSC (differential scanning calorimetry), energy dispersive X-ray diffractometry (EDX), and SEM (scanning electron microscopy) in the present work. The results indicated that with homogenization temperature increasing, the grains enlarged and the secondary phases dissolved into matrix gradually. The residual phase was Fe-rich particle after the alloy homogenized at 550 °C for 24 h and Zr-containing particle with larger size precipitated. While grains of the alloy with almost no change were observed after double-stage homogenization treatment, and the phases dissolved into matrix completely and Zr-containing particle with smaller size precipitated. Meanwhile the size of Zr-containing particle changed little with prolongation of second-stage time. The ideal homogenization process for the alloy was to homogenized at 430 °C for 10 h, subsequently followed by 550 °C for 24 h.

Lizhen Yan, Yong-An Zhang, Baiqing Xiong, Xiwu Li, Zhihui Li, Hongwei Liu, Shuhui Huang, Hongwei Yan, Kai Wen
Title
High Performance Structural Materials
Editor
Prof. Yafang Han