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Edited Proceedings


Additive Forming of Components — Tailoring Specific Material Properties in Low Volume Production

Anisotropic Mechanical Properties in a Big-Sized Ti-6Al-4V Plate Fabricated by Electron Beam Melting

In this study, in order to realize the application of the electron beam melting (EBM) technology for the printing of large components, the microstructure and mechanical properties of a big-sized Ti-6Al-4V plate (6 mm×180 mm×372 mm) additively manufactured by EBM were investigated. The paper focused on the graded microstructure and anisotropic mechanical properties by using x-ray diffraction, optical microscope, scanning electron microscope, microhardness and tensile test. A gradual change in microstructure with an increase in build height was observed. The formation of a graded microstructure was observed and discussed based on the thermal history experienced during printing. The mechanical properties were influenced accordingly by the graded microstructure. Moreover, the specimens which were printed parallel and perpendicular to the printing directions exhibited high elongation of ~18% and ~14%, respectively. The anisotropy in ductility was also observed and discussed according to the columnar prior β structure and grain boundary α phases present.

Pan Wang, Mui Ling Sharon Nai, Xipeng Tan, Wai Jack Sin, Shu Beng Tor, Jun Wei

Characterization of Microstructure and Mechanical Properties of Direct Metal Laser Sintered 15–5 PH1 Stainless Steel Powders and Components

15–5 PH1 stainless steel powder is one of the common materials used for the DMLS process. In this study, both the powder and parts fabricated via DMLS have been characterized. The microstructure and elemental composition have been examined. The microhardness and surface roughness have also been measured. The results show that most powder particle are in spherical with a particle size of 5 ~ 60 μm. Chemical compositions of the powder compare well with the literature data. The thickness of rough surface is about 1 μm. The measured Rockwell hardness is HRC 42.9±0.3, which is also in good agreement with literature.

Jing Zhang, Yi Zhang, Xingye Guo, Weng Hoh Lee, Bin Hu, Zhe Lu, Yeon-Gil Jung, Je-Hyun Lee

Materials Research in Reduced Gravity

Effect of Thermal Drift on the Initial Transient Behavior in Directional Solidification of a Bulk Transparent Model Alloy

In situ monitoring of directional solidification experiments on a transparent model alloy was carried out under low gravity in the Directional Solidification Insert of the Device for the Study of Critical Liquids and Crystallization (DECLIC-DSI) on-board the International Space Station. The present work is focused on the analysis of the interface recoil and its macroscopic shape evolution. Theoretically the interface movement is due to the formation of a solute boundary layer in front of the interface. However, the bulk configuration and the thermal specificities of transparent systems induce thermal effects, which are usually not observed in the classical thin sample configuration. Numerical thermal modeling highlights two thermal contributions to the interface recoil, both increasing with pulling rate. The Warren and Langer model is modified to take into account these contributions that modify the interface dynamics, and a good agreement is obtained between the experiments and the modified model.

F. L. Mota, N. Bergeon, D. Tourret, A. Karma, R. Trivedi, B. Billia

Rapid Quench in an Electrostatic Levitator

The Electrostatic Levitation (ESL) Laboratory at the NASA Marshall Space Flight Center (MSFC) is a unique facility for investigators studying high-temperature materials. The ESL laboratory’s main chamber has been upgraded with the addition of a rapid quench system. This system allows samples to be dropped into a quench vessel that can be filled with a low melting point material, such as a gallium or indium alloy, as a quench medium. Thereby allowing rapid quenching of undercooled liquid metals. Up to eight quench vessels can be loaded into a wheel inside the chamber that is indexed with control software. The system has been tested successfully with samples of zirconium, iron-cobalt alloys, iron-chromium-nickel, titanium-zirconium-nickel alloys, and a silicon-cobalt alloy. This new rapid quench system will allow materials science studies of undercooled materials and new materials development. The system is described and some initial results are presented.

Michael P. SanSoucie, Jan R. Rogers, Douglas M. Matson

Simulation of shrinkage-induced macrosegregation in a multicomponent alloy during reduced-gravity solidification

Segregation is a key phenomenon responsible for altering alloys’ properties during solidification. The factors that lead to solute partitioning at the scale of the solidified parts are related to movements of liquid and solid phases. However, when considering a reduced gravitational field, convection forces become less significant compared to other factors. Consequently, predicting segregation in this context requires considering other prevailing driving forces, namely solidification shrinkage that arises from the density difference between the liquid and solid phases. We propose a numerical model that accounts for energy conservation via a thermodynamic database, together with fluid momentum conservation and species conservation to predict segregation driven by solidification shrinkage in a multicomponent alloy. We apply it on a specific steel grade for which reduced-gravity experiments were performed via parabolic flights.

Ali Saud, Charles-André Gandin, Michel Bellet, Thomas Volkmann, Dieter Herlach

In Situ Investigation of the Effects of Gravity Level Variations on the Directional Solidification Microstructures During Parabolic Flights

In the framework of an ESA-MAP project entitled XRMON, directional solidification experiments of Al — 20 wt% Cu with in situ and real-time X-ray radiography were carried out during Parabolic Flight campaigns. Parabolic flights offer successions of periods with different gravity levels, allowing the investigation of the impact of gravity level variations on the solidification microstructure formation. Directional solidifications of refined Al — 20 wt% Cu alloy were investigated in a dedicated apparatus for a wide range of cooling rates and a constant temperature gradient. X-ray radiography was successfully used to observe the microstructure evolution following the variations of gravity level. During the columnar growth of the refined alloy a sharp increase of gravity level provoked the sudden nucleation of numerous grains ahead of the front. The most potent explanation of this effect is the variation of the liquid undercooling ahead of solid/liquid interface due to the changes of hydrostatic pressure in the melt.

L. Abou-Khalil, G. Salloum-Abou-Jaoude, G. Reinhart, C. Pickmann, G. Zimmermann, Y. Houltz, J. Li, O. Janson, H. Nguyen-Thi

Microstructural Evolution in Undercooled Al–8wt%Fe Melts

Containerless rapid solidification of hypereutectic Al–8wt%Fe is investigated experimentally using the Impulse Atomization technique (IA), as well as ElectroMagnetic Levitation (EML) under terrestrial and reduced gravity conditions. The samples were analyzed using scanning and transmission electron microscopy, X-ray and neutron diffraction, as well as electron backscattered diffraction. In both EML and IA, the samples experience some undercooling for the solidification of the primary intermetallic phase, which is likely metastable AlmFe (m = 4.0–4.4). After recalescence, the solidification path then continues with the nucleation and growth of stable Al13Fe4. While Al13Fe4 dominates in EML samples, it becomes minor in favor of AlmFe in IA droplets. The morphology differences of the primary intermetallics growing under terrestrial and microgravity conditions in EML are clear with acicular morphology for the former and a star-like morphology for the latter. The α–Al has a strong texture in microgravity EML and in IA samples while a weak one is observed on terrestrial EML. This difference is attributed to the weaker fluid flow occurring under reduced gravity conditions and in IA droplets.

J. Valloton, A. A. Bogno, J. Chen, R. Lengsdorf, H. Henein, D. M. Herlach, U. Dahlborg, M. Calvo-Dahlborg

Metal and Polymer Matrix Composites II

Degradation Study of High Melt Strength Polypropylene/Clay Nanocomposites in Environmental and Accelerated Conditions

The Polypropylene (PP) was initially modified by γ radiation or high melt strength PP. HMS-PP/ Cloisite 20 nanocomposites processed by melt mixing in twin-screw extruder derived samples to evaluate under environmental and thermal degradation conditions. PP-g-MA was the compatibilizing agent. The tests were conducted on dumbbell shaped samples under two different ageing conditions of degradation: environmental exposition and accelerated exposition. The morphology of aged samples was evaluated by XRD. TEM microscopy showed intercalation and exfoliation. Thermal degradation was studied by TGA. The DSC and the results showed decrease of melting point and increased crystallization under ageing conditions. The FTIR results showed the increase of carbonyl index related to the surface oxidation of the nanocomposites.

Luiz Gustavo Hiroki Komatsu, Duclerc Fernandes Parra, Washington Luiz Oliani, Ademar Benevolo Lugao, Vijaya Kumar Rangari

Nanotube Sheet — Graphite Hybrid Nanocomposite for Damage Detection

In this study, we fabricate carbon nanotube (CNT) sheet — graphite powder hybrid nanocomposites and determine their strain dependent electrical resistivity for applications in damage sensing of aerospace composites. CNT sheet — graphite powder nanocomposites are prepared by epoxy resin infiltration under vacuum followed by oven curing. The electrical resistivity of the composites is measured while simultaneously subjecting it to tensile loading. The resistivity of the nanocomposite films without load reduces from about 34.7×10–5Ω·m to 8.1×10–5Ω·m by the addition of varying quantities of graphite powder. Additionally, the change in resistivity with tensile strain shows a significant improvement from 0.85 x10–5Ω·m to 8.9x10–5Ω·m when epoxy resin is modified with 5 wt% graphite powder. There is an associated particle size effect. The improvements are observed only when the second phase is graphitic particles (300 – 1000 µm) and not for fine graphene flakes (0.5 – 3 µm). We propose the application of these nanocomposites in damage sensing of aerospace carbon-fiber composites.

Jiukun Li, Sirish Namilae

Effect of Nano-Particle Addition on Grain Structure Evolution of Friction Stir Processed Al 6061 During Post-Weld Annealing

The fabrication of nano-composites is quite challenging because uniform dispersion of nano-sized reinforcements in metallic substrate is difficult to achieve using powder metallurgy or liquid processing methods. In the present study, Al-based nano-composites reinforced with Al2O3 particles have been successfully fabricated using friction stir processing. The effects of nano-Al2O3 particle addition on grain structure evolution of friction stir processed Al matrix during post-weld annealing were investigated. It was revealed that the pinning effect of Al2O3 particles retarded grain growth and completely prevented abnormal grain growth during post weld annealing at 470 °C. However, abnormal grain growth can still occur when the composite material was annealed at 530 °C. The mechanism involved in the grain structure evolution was discussed therein.

Guo Junfeng, Lee Bing Yang, Du Zhenglin, Bi Guijun, Tan Ming Jen, Wei Jun

Enhanced Ductility with Significant Increase in Strength of As-Cast CNTs/AZ91D Nanocomposites

This paper was focused on significantly increasing the ductility and strength of as-cast CNTs/AZ91D nanocomposites by solid solution (T4) and aging treatment (T6). The CNTs/AZ91D nanocomposite fabricated by permanent gravity casting assisted with ultrasonic processing was subject to as-cast, T4 and T6 treatment and the mechanical properties were tested. The results showed that the ductility and the tensile strength of the nanocomposites after T4 treatment were increased by 23.8 percent and 82.8 percent compared with the as-cast properties. After T6 treatment, the tensile strength and especially the yield strength of the nanocomposites was increased by 26.2 and 17.6 percent, while its ductility was still increased by 20.7 percent. The strengthening and toughing mechanisms of the nanocomposites were discussed based on the microstructure characterization results.

Rongyu Feng, Lin Zhu, Wenzhen Li

The Synthesis and Processing Self-Healing Structural Al/Mg Lamellar Composite Materials

Self-healing alloy composites have been designed to address the need for self-repairable high-strength materials. However, delamination and cracking is a major limitation, stitching, and healing is established via the synergetic effect of low melting phase, Zn, and alloying element segregation. Under the controlled parameters, polycrystalline double layers are grown experimentally at the interfacial contacts between Al-Mg foils. The growth behavior of the interphase layers characterizing interface motion and long-range diffusion is established. The kinetic of controlled interphase with stitching/bridging and healing mechanism is introduced with microstructural and mechanical characterization. Chemical and mechanical bonding via inter diffusion processing with alloy segregatio are dominant for inte rphase kinetics. SEM, EDX and tensile testing with interfacial shear strength are introduced. The interphase kinetic established through localized micro plasticity, metal flow, alloy segregation and delocalized Al oxide and Mg oxide. The kinetic of interface/interphase introduce new nontraditional self-healing composite with new bridging and shielding mechanisms.

Yasser Fouad, Bakr Mohamed Rabeeh

Filler Surface Nature, Bead, Solution Viscosity and Fibre Diameter of Electrospun Particle-Reinforced Polylactide

The effect of viscosity of agro particle reinforced polylactide (PLA) solution on the electrospun fibre diameter and bead size produced is examined. Solutions of agro waste particle reinforced PLA were made at varying filler weight fraction and these electrospun into fibres. A scanning electron microscope was used to examine the morphologies of fibres while the fibre diameters were determined using ImageJ software. Results show that solution viscosity does not affect fibre diameter when agro particle fillers are processed by a combination of mechanical, thermal and chemical treatments prior to been used as reinforcement. At lower concentration of reinforcement, beads generated from treated particles were of smaller diameter. High solution viscosity gave rise to large bead diameters for treated and untreated reinforcements. Thus, the effect of solution viscosity on fibre and bead diameters depends largely on surface nature of the agro filler.

S. O. Adeosun, E. I. Akpan, O. P. Gbenebor, A. A. Peter, S. A. Olaleye

Evaluation of Intermetallic Reaction Layer Formation Within Steel Encapsulated Metal Matrix Composites

Macro hybridized systems consisting of steel encapsulated light metal matrix composites (MMCs) deliver a low cost/light weight composite with enhanced mechanical properties. By exploiting the high strength, modulus, and damage tolerance of steels and the high stiffness and low density of MMCs the resultant macro hybridized systems alleviates the high density of steel and the poor ductility of MMCs. The resultant system, when properly designed, offers higher specific properties and a more structurally efficient system can be attained. However, the combination of these dissimilar materials, specifically iron and aluminum, often results in the formation of intermetallic compounds. In certain loading situations, these typically brittle intermetallic layers can result in degraded performance. In this research, X-ray Diffraction (XRD), X-ray Energy Dispersive Spectroscopy (EDS), and Electron Backscatter Diffraction (EBSD) are utilized to characterize the intermetallic reaction layer formed between an aluminum or magnesium MMCs reinforced with Al2O3, SiC, or B4C particles and encapsulated by A36 steel, 304 stainless steel, or Nitronic® 50 stainless steel.

Sean Fudger, Eric Klier, Prashant Karandikar, Chaoying Ni

Effect of Load and Grit Size on High Stress Abrasive Wear of Al-Mg-Si Hybrid Composites

In the present investigation, the two body abrasive wear behavior of Al-6082 alloy, Al 6082–10% SiC (Al-SiC) composites & Al 6082–5%SiC-5%Gr (Al-SiC-Gr) hybrid composites was studied at load of 5–15N, 75m sliding distance and abrasive grit size of 100–200um by using pin-on-disc equipment. The composites were synthesized by stir casting technique, a liquid metallurgy route. It was observed that load and type of emery paper used would have profound influence on the abrasive wear characteristics in the present set of experiments. The results show that graphitic composites yielded better wear resistance compared to alloy and SiC alone reinforced composites. At higher load and abrasive grit size, 16.4% and 11.6% improvement was observed for Al-SiC-Gr and Al-SiC composites respectively when compared to unreinforced alloy. Worn surface analysis of tested samples and tested grit papers were observed by using scanning electron microscope (SEM).

Kaushik N Ch, Narasimha Rao R

The Corrosion of 30% Mo-ZrO2 Cermet in Molten Slag of CaO-MgO-Al2O3

Mo-ZrO2 cermet is a potential material for application as electrode in steel purifying process with addition of electrical field because of its high electrical conductivity and good corrosion resistance to molten slag and steel at high temperature. This paper describes the static corrosion test of Mo-ZrO2 cermet sample with Mo content 30 vol.% in CaO-MgO-Al2O3 molten at 1550°C The results showed that a dense CaZrO3 layer was formed during test and it will prevent the further corrosion of cermet by slag.

Xiaopeng Li, Ziming Wang, Yang Yang, Yanling Guo, Jieyu Zhang, Wende Dan

Study on Mechanical Property of Porous Titanium by Adding Powder Carbon

Titanium alloys have a wide variety of applications in the aerospace, automotive and biomedical industries. Furthermore, titanium carbide (TiC) has been used for reinforcement of titanium alloy matrices due to its compatibility.In this paper, under the experimental condition of 0.1 Pa, the sintering temperature of 1250°C and sintering time of 2h, the porous titanium is fabricated by powder metallurgy blend element method. The conclusions manifest that porosity has a decreasing trend with increasing the addition of carbon; however, apparent increase of porosity appears when the addition of carbon increases to 2.5 wt%. The TiC is generated in the matrix manifested from the detection results of XRD. When the carbon content achieves 1.5 wt% and 2.0wt%, the initial yield strength reaches the highest with 339.8±15MPa and 331.1±10MPa separately. When the content of carbon powder achieves 2.5 wt%, the initial yield strength decreases to 195.1±15MPa.

Guibao Qiu, Hao Cui, Tengfei Lu, Yilong Liao, Yang Yang

Fabrication of Gamma-Irradiated Polypropylene and AgNPs Nanocomposite Films and Their Antimicrobial Activity

Polymer nanocomposite films of polypropylene and AgNPs were prepared by melt extrusion using twin-screw extruder. These polymer nanocomposites were further modified by y-irradiation in acetylene at dose of 12.5 kGy The AgNPs (silver nanoparticles) used in this study were synthetized using sonochemical method from silver nitrate precursor. The polymer nanocomposites were evaluated using differential scanning calorimetry (DSC), X-Ray diffraction (XRD), FTIR spectroscopy and Scanning electron microscopy (SEM). We have also studied the antibacterial activity of these polymer nanocomposite films against two different groups of bacteria-Staphylococcus aureus (S. aureus; gram-positive bacteria) and Escherichia coli (E. coli; gram-negative bacteria).

Isabelle Oliveira Berenguer, Washington Luiz Oliani, Duclerc Fernandes Parra, Luiz Gustavo Hiroki Komatsu, Vinicius Juvino dos Santos, Nilton Lincopan, Ademar Benevolo Lugao, Vijaya Kumar Rangari

Natural Aging Effects in HMS-Polypropylene Synthesized by Gamma Radiation in Acetylene Atmosphere

High melt strength polypropylene (HMSPP) is produced by y-radiation process to improve the melt viscosity suitable for melt blow film process. The melt strength (MS) properties of a polymer increases with molecular weight and with long chain branching due to the increase chain entanglement levels in the polymer. The main scope of this study is to evaluate the stability of HMSPP prepared by gamma radiation with doses of 5, 12.5 and 20 kGy in comparison with virgin PP. The samples were subjected to the natural aging for a period of one year. These polymers were characterized by: Thermogravimetry analysis (TGA), Differential scanning calorimetry (DSC), Infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). These results show predominantly chain scissions degradation mechanism, owing to the reactivity of the tertiary carbon of macro chains. The chemi-crystallization caused by degradation processes (thermal and photodegradation) was detected in HMSPP.

Washington Luiz Oliani, Luiz Gustavo Hiroki Komatsu, Ademar Benevolo Lugao, Vijaya Kumar Rangari, Duclerc Fernandes Parra

Superaligned Carbon Nanotubes Reinforced Copper Nanocomposites with Enhanced Strength and Electrical Conductivity

A new kind of laminar metal matrix nanocomposite was fabricated by an electroplating process with copper and superaligned film of carbon nanotubes (SACNT film). We put the SACNT film on a titanium plate and then electroplated a layer of copper on it. By repeating the above process, we could get the laminar Cu/SACNT composite which contains dozens or hundreds layers of copper and SACNT films. The thickness of a single layer could be controlled by the electroplating parameter easily. Microscopic observation showed that the directional alignment structure of SACNT has been retained in the composite perfectly. Mechanical and electrical properties testing results showed that tensile and yield strengths of composites improve obviously compared to pure copper and retain the high conductivity. This technology is a potential method to make applicable MMC which characterizes directional alignment of carbon nanotubes.

Jing Shuai, Yu Jin, Lin Zhu, Wenzhen Li

Unedited Proceedings


Additive Manufacturing: Building the Pathway towards Process and Material Qualification

Selective Laser Melting of TiB2/H13 Steel Bulk Nanocomposites: Influence of Nanoscale Reinforcment

Additive Manufacturing (AM) holds strong potential for the formation of a new class of multifunctional nanocomposites. Selective laser melting, as a promising AM fabrication route, was applied to produce nanocrystalline TiB2-reinforced H13 steel matrix nanocomposites. Uniformly dispersed TiB2 particles were obtained and fine homogenous needle-shaped martensitic microstructures were observed. The microstructural and hardness of SLM-processed nanocomposites were sensitive to the TiB2 addition. Relative to the unreinforced H13 steel part, the TiB2/ H13 steel nanocomposites parts with the novel architecture exhibited much higher hardness due to the combined effects of grain refinements and grain boundary strengthening.

B. Almangour, Dariusz Grzesiak, J. M. Yang

In-Space Manufacturing Baseline Property Development

The In-Space Manufacturing (ISM) project at NASA Marshall Space Flight Center currently operates a 3D FDM (fused deposition modeling) printer onboard the International Space Station. In order to enable utilization of this capability by designer, the project needs to establish characteristic material properties for materials produced using the process. This is difficult for additive manufacturing since standards and specifications do not yet exist for these technologies. Due to availability of crew time, there are limitations to the sample size which in turn limits the application of the traditional design allowables approaches to develop a materials property database for designers. In this study, various approaches to development of material databases were evaluated for use by designers of space systems who wish to leverage in-space manufacturing capabilities. This study focuses on alternative statistical techniques for baseline property development to support in-space manufacturing.

Tom Stockman, Judith Schneider, Tracie Prater, Quincy Bean, Nicki Werkheiser

Using Powder Cored Tubular Wire Technology to Enhance Electron Beam Freeform Fabricated Structures

Electron Beam Freeform Fabrication (EBF3) is an additive manufacturing technique, developed at NASA Langley Research Center, capable of fabricating large scale aerospace parts. Advantages of using EBF3 as opposed to conventional manufacturing methods include, decreased design-to-product time, decreased wasted material, and the ability to adapt controls to produce geometrically complex parts with properties comparable to wrought products. However, to fully exploit the potential of the EBF3 process development of materials tailored for the process is required. Powder cored tubular wire (PCTW) technology was used to modify Ti-6Al-4V and Al 6061 feedstock to enhance alloy content, refine grain size, and create a metal matrix composite in the as-solidified structures, respectively.

Devon Gonzales, Stephen Liu, Marcia Domack, Robert Hafley

Microstructure Evolution of Martensitic Stainless Steel in Laser Hot Wire Cladding With Multiple Heating Passes

Laser cladding is one of attractive and cost effective means for repairing or remanufacturing high value engineering components. The microstructure and property in laser cladding process with multiple heating passes were investigated by using experimental method. Single-pass cladding experiments were conducted to investigate the wire transfer behavior and further optimize the laser hot wire cladding process. Multiple layers were cladded on the surface of martensite stainless steel by using fiber laser. The microstructure of clad layer and heat affected zone was characterized using an optical microscope, SEM and EDS. The orientation imaging microscopy of grain structure was obtained by the electron backscatter diffraction technique. The gradient microhardness from the clad layer to the substrate was tested. The uneven temperature distribution and high cooling rate led to the forming of gradient microstructure, and further affect the mechanical property of the remanufacturing parts.

Shaopeng Wei, Gang Wang, Zhenguo Nie, Zilin Huang, Yiming Rong

Effect of Printing Orientation on Strength of 3D Printed ABS Plastics

The mechanical strengths of ABS (Acrylonitrile Butadiene Styrene) components fabricated by fused deposition modeling (FDM) technique have been studied, with the focus on the effect of printing orientations on the strength. Using the properties derived from stress-strain curves of the samples, the 0-degree printed sample has the strongest mechanical properties, which is likely due to preferred orientations in individual slice.

Linlin Cai, Philip Byrd, Hanyin Zhang, Kate Schlarman, Yi Zhang, Michael Golub, Jing Zhang

Verification of Numerically Calculated Cooling Rates of Powder bed Additive Manufacturing

In order to increase the powder bed production rates, the laser power and diameter are increased enabling faster scanning, thicker powder layers and wider hatches. These parameters however interact in a very complex manner: For example increasing the laser power may lead to significant evaporation of the molten metal. Increasing the scan speed may lead to reduced melting and lack of fusion of the powder particles. Combining higher scanning speeds with increased layer thickness enhances lack of fusion even more. Larger beam diameters reduce the energy density and hence impose limitations to scan speeds. Physics based modelling has the potential to shed light into how these competing phenomena interact and can accelerate fine tuning build parameters to achieve design goals. Models resolving the heat source powder interaction and describing the melt pool and solidification processes could not be formally validated using experimental data due to the extreme severity of the processing environment. In an effort to verify models describing melt pool behavior the results of two different algorithms are compared: Lattice Boltzmann and Finite Volume Computational Fluid Dynamics. Both codes were developed separately by two different and independent teams. A reference benchmark is defined with corresponding operation conditions. The physical assumptions are aligned as far as possible. The melt pool characteristics and the thermal cycles are compared.

H.-W. Mindt, M. Megahed, N. P. Lavery, A. Giordimaina, S. G. R. Brown

Advanced Materials in Dental and Orthopedic Applications

Beta-Type Titanium Alloys for use as Rods in Spinal Fixation Devices

Ti-12Cr has been developed for use in various biomedical applications, in particular; it is expected to be used for the rods of the spinal fixation devices. When Ti-12Cr is deformed, its Young’s modulus increases because of deformation-induced ω phase transformation. If a spinal rod made of Ti-12Cr is bent during operation, only the Young’s modulus of the bent region will increase; this phenomenon decreases the springback of the rod so that the bent shape is maintained. The compression fatigue strength of Ti-12Cr obtained from compression fatigue tests performed according to ASTM F1717 can be significantly improved by cavitation peening. Details of the development of this Ti-Cr alloy for use as spinal rods are discussed.

Mitsuo Niinomi, Masaaki Nakai, Huihong Liu, Kengo Narita

Effect of MMT Nanoparticle Clay on Flexural Properties of Polymer Based BisGMA/TEGDMA Resin

The objective of this study is to evaluate the (strength and modulus) and degree of conversion of dimethacrylate resin containing different amounts of Montomorillonite (MMT) Cloisite 20A nanoclay as filler. Eight formulations of polymer based BisGMA/TEGDMA (four with MMT and another four with barium glass (BG) as filler) at concentration of 20, 30, 40 and 50% by weight were studied. As control, a series of composites containing BG particles were also tested. The flexural strength data was analyzed using Kruskal-Wallis and Tukey’s tests. The addition of MMT nanoparticles in a BisGMA / TEGDMA resin matrix resulted in similar degree of conversion and higher elastic modulus values compared to the groups filled with BG. The decrease in the resistance value with increasing concentration of MMT may be due to the formation of agglomerates (clusters) that decreases the reinforcement efficiency.

Duclerc Parra, Luiza Campos, Letícia Boaro, Henrique Ferreira, Ademar Lugão, Vijaya Rangari

Fatigue Performance of New Developed Biomedical Ti-15Mo Alloy with Surface Modified by TiO2 Nanotubes Formation

In recent years, it was demonstrated that Ti-Mo alloys are promising to be use as orthopedic implants. The presence of TiO2 nanotubes can increase the bioactivity and improve the osseointegration of Ti and its alloys implants, although this modification could lead to a reduction in the dynamic mechanical properties. In this context, the purpose of the present study was to obtain self-organized nanotubes on the surface of biomedical Ti-15Mo alloy and verify whether the fatigue performance was significantly changed. Organized nanotubes were obtained by anodic oxidation using ethylene glycol + NH4F solution. The axial fatigue behavior was characterized by stepwise increases of the applied load in air and in physiological media at 37°C. The results was compared with the as-polished samples in order to compare if the Ti-15Mo alloy fatigue behavior was affected by the surface modification, and it was found that the mechanical performance of the Ti-15Mo alloy was affected by the surface modification, in that specific experimental conditions used to obtain the nanotubes.

Nilson T. C. Oliveira, Leonardo C. Campanelli, Carolina C. Bortolan, Claudemiro Bolfarini

Computational Materials Discovery and Optimization: From 2D to Bulk Materials

First Principles Investigation on TiAl3 Alloys Substitutively Doped with Si

The site preference of Si in TiAl3 is calculated using first principles method based on Density Functional Theory. Through the analyses and comparison of the binding energy of systems with different substitution behaviors, it is shown that Si prefers to occupy the site of Al(2) and the limited solubility of Si in TiAl3 is around 12.5%. Then this article made a research on the antioxidant properties of different doped concentration of Si in TiAl3, and the result showed that the Si doping enhanced the oxidation resistance of the Ti-Al alloy.

Qing Du, WeiDong Hu, WangJun Peng, GuangXin Wu, WenDe Dan, JieYu Zhang

Effect of Strain on the Physical Properties of Lanthanum Nickelate

Lanthanum nickelate (LaNiO3) is a promising material for stable fuel-cell electrode, optoelectronic and magneto-electronic devices. Density functional theory (DFT) based calculations were carried out to investigate the effect of strain on the physical properties of the correlated metal LaNiO3. Electronic structure, optical conductivity and temperature variation of resistivity have been studied in detail using GGA+U approach. It has been observed that LaNiO3 under strain is more metallic compared to the unstrained system. However LaNiO3 under compressive strain is found to be more metallic than that under tensile strain. Electron localization function calculation revealed that LaNiO3 under tensile strain has more covalent bonding than that under compressive strain, which results in an increase in resistivity for the system under tensile strain. The theoretical understanding of the alternation of physical properties of the system, caused by misfit strain may help in the application of the system in different device purposes using strain engineering.

D. Misra, T. K. Kundu, Ankit

Hydrogen-Induced Core Structures Change of Screw and Edge Dislocations in Tungsten

A Quantum Mechanic/ molecular mechanical (QM/MM) method is employed in studying the screw and edge dislocation core structure of Tungsten. When absence of H, the widely used MEAM potential can successfully provide the core structure for both types of dislocations. However, no suitable W-H potential can describe the right structure when H is introduced. The coupling of the molecular dynamics and Ab initio calculation predicts a six-fold nondegenerate structure with a H atom added in screw dislocation, while in edge dislocation a partial dislocation appeared in the dislocation core.

Yinan Wang, Chengliang Li, Ben Xu, Wei Liu

Computational Materials Engineering for Nuclear Reactor Applications

Validation of BISON Calculation of Hydrogen Distribution by Comparison to Experiment

During normal operation in nuclear reactors, the nuclear fuel cladding corrodes as a result of exposure to high temperature cooling water. During this process, hydrogen can enter the zirconium-alloy of the fuel cladding, and under proper conditions, precipitate as brittle hydride platelets which can severely impact cladding ductility and fracture toughness. Hydrogen tends to migrate to and precipitate at colder spots. Because high local hydride concentrations increase the risk of cladding failure, it is important to predict the local hydrogen distribution. To that end, a hydrogen transport model has been implemented in the 3D fuel performance code BISON. In this study, we present an initial attempt of using this model for benchmarking the BISON code as applied to a case of the hydrogen distribution measured in a nuclear fuel rod, which had undergone a five cycles exposure. The prediction of hydrogen distribution show good agreement with the post irradiation measurement, indicating the promise of this benchmarking method.

Evrard Lacroix, Arthur Motta

Computational Methods for Uncertainty Quantification, Model Validation, and Stochastic Predictions

Effect of K-Point Convergence on Derived Properties for Pure Crystals

In planewave DFT calculations, a number of parameters have an effect on the overall accuracy of the calculation. Typically, a few of these parameters are under user control and have a significant effect. In this proceeding paper, these effects are explored through calculations of an fcc Al model system. The convergence of the total energy and several derived properties (e.g. unit cell volume and bulk modulus) is assessed with respect to the number of k points used to sample the Brillouin zone and the magnitude of the smearing parameter. Results are compared to those computed using the tetrahedron method. It is seen that some properties converge quickly with respect to the varied parameters, while others are more sensitive.

Thomas C. Allison

Quantifying Model-Form Uncertainty in Molecular Dynamics Simulation

The accuracy of the interatomic potential models plays a vital role toward the reliability of molecular dynamics (MD) simulation prediction. These interatomic potentials, which are the main source of model-form uncertainty in MD, are inherently imprecise due to errors in experimental measurement or first-principles calculation. Existing studies of uncertainty effect in MD simulation use non-intrusive uncertainty quantification (UQ) methods. In this work, a reliable MD (R-MD) mechanism as an intrusive UQ approach is developed. In R-MD, the locations and velocities of particles are not assumed to be precisely known, as a result of imprecise interatomic potentials. They have interval values. Kaucher arithmetic is applied for propagating uncertainty. Sensitivity can be efficiently analyzed with the calculated lower and upper bounds. The new simulation mechanism for isothermal-isobaric ensemble is implemented for demonstrations. The advantage of this approach is that uncertainty effect can be assessed on-the-fly with only one run of simulation.

Anh V. Tran, Yan Wang

Atomistic Study of Carbon Nanotubes: Effect of Cut-Off Distance

Carbon nanotubes (CNTs) superiority have been proved by many experiments and studies. Molecular Dynamics was vastly used by many researchers to analyze properties of CNTs in atomistic scale with various interaction potentials (Force fields). Most of the carbon based interaction potentials were parameterized with cut-off function used to truncate potential energy between certain inner and outer cut-off interatomic distance. These values are having major effects on the mechanical properties. Improper cut-off values may leads to under or over coordination in interaction between two atoms which will exhibits the non-physical behaviours in properties. Most of the researchers have attempted to change outer cut-off value to avoid the non-physical behavior arises during uniaxial tensile studies, those approaches were end up with under coordination between atoms. This paper mainly deals about effect of cut-off distance used in Molecular Dynamics study for analyzing the mechanical properties of CNTs based on AIREBO potential.

S. Thamaraikannan, S. C. Pradhan

Bayesian Calibration of a Physical Model for Plastic Flow Behavior of Trip Steels

Rivera’s physical model [Modeling Simul. Mater. Sci. Eng. 22 (2014) 015009 (22pp)] based on irreversible thermodynamics of dislocation evolution has been used in this work to predict the stress-strain behavior of TRIP steels during plastic deformation. This model has been applied to account for plastic deformation of individual phases, and the iso-work approximation has been used as a homogenization framework to simulate the behavior of the composite system. Contribution to plastic behavior due to strain-induced martensitic transformation in austenite has also been taken into account. Calibration and analysis of parameter uncertainty is performed using a Bayesian method based on Metropolis-Hastings Markov Chain Monte Carlo algorithms. Using this approach, the model has been trained with different experimental data to estimate parameters and their uncertainties. The parameter posterior probability distribution obtained from is considered as the prior probability distribution for subsequent training. The stress-strain curves obtained from the model with new estimated parameters show good agreement with the experimental data in literature.

P. Honarmandi, R. Arroyave

Computational Thermodynamics and Kinetics

Homogeneous Nucleation and Inner Structure Evolution in Nucleus Fe from Classic Molecular Dynamics Simulation

Molecular dynamic simulation was used to study the solidification process of liquid Fe with Sutton-Chen potential. Bond orientational order (BOO) parameters and Voronoi polyhedron index (VPI) method, named BOO+VPI method, were applied to identify atomic local structure and local volume precisely. During the solidification process, two large clusters were detected, one is an imperfect five-fold twinning structure, and the other is a lamellar structure. In addition, the density and order of the two clusters were analyzed along with their growth. All analyses suggest that the density and the order of the crystal nucleus increase gradually with the increase of the size, and the order of the crystal nucleus with the five-fold twinning structure is higher. Meanwhile, the embryos are always found in high structure-ordered region instead of high density region.

Jie Luo, Junjiang Xiao, Yongquan Wu

Anisotropy of Crystal-Melt Interface of BCC-Fe and FCC-Fe from Molecular Dynamics Simulation

Thermodynamic and kinetic properties of crystal-melt (c-m) interface were computed for both BCC and FCC phases of Fe by molecular-dynamics simulation. Two Sutton-Chen potentials were adopted to describe the two solid phases of Fe. Firstly discussed is the anisotropy of melting point in different interfacial orientation which is calculated by two different methods (the coexisting phase method(CPM) and the interfacial velocity methods(IVM)). Free solidification simulations were used to determine the kinetic coefficient μ of the c-m interface. The anisotropy of of μ with respect to growth direction is μ 100 > μ110, μ100 > μ111 for the BCC phase and μ100 > μ110 ~ μ111 for the FCC phase, and the kinetic coefficients of BCC are larger than the counterparts for he FCC. Through the interfacial roughness of BCC-Fe under supercooling/superheating, the slight asymmetry between melting and solidifying can be observed too.

Linlin Lv, Yewei Jiang, Yongquan Wu, Junjiang Xiao

Thermal Decomposition Kinetics of Manganese Carbonate in the Process of MnZn Ferrite Preparation

Thermogravimetric analysis method was used to study the decomposition of MnCO3 in the process of MnZn ferrite preparation. The effects of different heating rate (5, 10, 20, 30 and 40 K· min-1) on the initial temperature and terminative temperature of the manganese carbonate decomposition were investigated. The Flynn-Wall-Ozawa method and Kissinger-Akahira-Sunose method were used to calculate the decomposition activation energy of manganese carbonate. The results show that the terminative temperature of manganese carbonate decomposition will increase with increasing of heating rate. The decomposition activation energy of manganese carbonate in the process of MnZn ferrite preparation calculated by FWO and KAS methods were 67.94kJ·mo l-1 and 64.31kJ·mo l-1, respectively. The decomposition activation energy of manganese carbonate in the process of MnZn ferrite preparation is lower than in another two systems.

Lin Wang, Yan-hong Li, Jin-lin LU, Wei XU, Hui-long Lin

Solid-Liquid Phase Transitions of FCC-Al and HCP-Mg Nanoparticles

We used molecular dynamics methods to simulate the melting and cooling of isolated fcc-Al and hcp-Mg nanoparticles with embedded-atom method (EAM) potentials. Bond orientational order (BOO) parameters and Voronoi polyhedron (VP) method were used to identify the local structure and local volume of each atom. The variation of energy was first analyzed to give an overview of the simulation. The inner structure evolution during the solidification was also investigated under different cooling rates. Two different inner structures, including five-fold twinning and lamellar structures, have been found in the cooling process of fcc-Al, while only lamellar structures for hcp-Mg.

Yewei Jiang, Linlin Lv, Yongquan Wu

A Discrete Dislocation Model of Creep in Single Crystals

We present a new computational approach for modeling dislocation creep in metals using kinetic Monte Carlo simulation of thermally activated dislocation glide, extending the discrete dislocation dynamics method of plasticity. The method is used to study the problem of power-law creep in precipitation strengthened Aluminum single crystals. The new model predicts creep rates and stress exponents consistent with their known ranges from experiments.

M. Rajaguru, S. M. Keralavarma

Study of the Temperature Effects on Solid-Liquid Anisotropic Interfacial Energy

In this work, a new method for calculating the solid-liquid interfacial energy was proposed by the combining of the classical nucleus method (CNM) and capillary fluctuation method (CFM). The anisotropy of interfacial energies of Al increases as the temperature drops, while the orientationally averaged interfacial energy shows no such kind of tendency.

L. K. Wu, C. L. Li, B. Xu, Q. L. Li, W. Liu

Application of MIVM for Sn-Ag and Sn-In Alloys in Vacuum Distillation

In this study, the vapor-liquid phase equilibrium compositions of tin-silver (Sn-Ag) and tin-indium (Sn-In) alloys in vacuum distillation were predicted based on the molecular interaction volume model (MIVM) and vacuum distillation theory, which can be used to precisely estimate the separation degree and the product composition in vacuum distillation. The calculated values of activities of components in Sn-Ag and Sn-In alloys are in good agreement with experimental data, which indicates that the method is reliable and convenient due to the MIVM has a clear physical basis and can predict the thermodynamic properties of multi-component liquid alloys using only two infinite dilute activity coefficients. This study provides an effective and convenient model on which to base refining simulations for Sn-based alloys.

Lingxin Kong, Junjie Xu, Baoqiang Xu, Shuai Xu, Bin Yang, Yifu Li, Dachun Liu, Ruibo Hu

Experiments and Kinetics Modeling for Gasification of Biomass Char and Coal Char under CO2 and Steam Condition

Gasification behaviors of biomass char and coal char were analyzed by thermal gravimetric method, and influences of gasification temperature and different gasifying agents were investigated. At the same time, kinetics of char gasification under CO2 condition and steam condition were investigated by Chou model. Under the same condition, gasification characteristics of biomass char are better than that of coal char, and meanwhile performance of steam is better than CO2 as gasifying agent. From kinetics analysis, among 1173~1323K range, gasification of biomass char and coal char is under chemical reaction control both for steam and CO2 condition. Gasification process of biomass char could be simulated by flat particle gas-solid reaction of Chou model, with activation energy as 113.7kJ/mol and76.4kJ/mol for CO2 and steam condition respectively; gasification of coal char could be simulated by spherical particle gas-solid reaction of Chou model, with activation energy 182.6kJ/mol and160.9kJ/mol for CO2 and steam condition respectively.

Guang-wei Wang, Jian-liang Zhang, Jiu-gang Shao, Peng-cheng Zhang

Optimization of Main Factors for Decarbonizing Ratio of TiB2 Powders by Reverse Flotation Using Response Surface Methodology

The optimization of process conditions for decarbonizing ratio of titanium dibordie (TiB2) powders by reverse flotation was investigated using response surface methodology (RSM). The TiB2 powders was produced by using a powder mixture of C, TiO2 and H3BO3 in a DC electric arc furnace. The carbon is in the form of graphite in the product. The way of carbon removal from the powder of TiB2 produce is reverse flotation. Three key parameters TiB2 size, slurry concentration and collector dosage were chosen as variables. The optimum process conditions for decarbonizing ratio were determined by analyzing the response surface three-dimension surface plot and contour plot and by solving the regression model equation with Design Expert software. The central composite design (CCD) of RSM was used to optimize the process conditions, which showed that TiB2 size of 20µm, slurry concentration of 29.65% and collector dosage of 400 g/t were the best conditions. Under the optimal conditions, the decarbonizing ratio is 87.65%, and the relative error differed by only 1.2% from the predicted values of model (88.72%).

Xiaoxiao Huang, Shuchen Sun, Shuaidan Lu, Kuanhe Li, Xiaoping Zhu, Ganfeng Tu

General Poster Session

A Novel Process for Treating with Low Grade Zinc Oxide Ores in Hydrometallurgy

A novel, hydrometallurgical process for treating with low grade zinc oxide ores was proposed in this paper. It contains three steps of treatment. Firstly, leaching of ores in alkalescent Ida2−-H2O system (iminodiacetate aqueous solution). Valuable metals such as Zn, Cu, Ni, Pb and Cd in ores will be dissolved in leaching liquor for their complexation with Ida2−, impurities such as Ca, Mg, Si and Fe will not be dissolved. Secondly, precipitation of Zn from leaching liquor by adjusting basicity with CaO. Zn will be precipitated as ZnO in residues for recovery. Thirdly, precipitation of Ca by adjusting acidity with CO2 in the solution after Zn precipitation. Ca which was accumulated in the second step will be removed as CaCO3 from the solution. The lixiviant will be reclaimed in the solution after Ca precipitation. The reclaimed lixiviant solution can be used for re-leaching of ores. The lixiviant solution had been regenerated for 5 times in the paper. The results showed that the performance of the regenerated lixiviant solution could be compared with the freshly prepared lixiviant solution.

Aichun Dou

A Study of Taguchi Method to Optimize 6XXX Series Aluminium Anodic Oxide Film’s Hardness and Investigation of Corrosion Behaviors of Oxide Films

This study is intended to present an efficient methodology for optimizing the anodic polarization process of 6xxx aluminum alloy to have high hardness. Additional electrochemical experiments have been conducted to observe the corrosion behavior of these oxide films. L9orthogonal array with four factors at three levelsareused. The type of additive, electrolyte temperature, current density and dissolved aluminum ions are chosen as parameters. The results show that the main parameters to increase the hardness of the oxide films are electrolyte temperature, additive type, dissolved aluminum ions and current density, respectively.After anodization, the pores of the oxide film are sealed and their surface morphologies are observed by using scanning electron microscopy. Then, the corrosion potentials of these oxide films are measured to define their electrochemical behaviors to evaluate their possible uses in advanced technology.

B. D. Polat, B. Bilici, P. Afşin, C. Akyil, O. Keles

Anticorrosion Performance of Solanum Aethiopicum on Steel-Reinforcement in Concrete Immersed in Industrial/Microbial Simulating-Environment

This paper investigates anticorrosion performance of Solanum aethiopicum leaf-extract on steel-reinforcement in concrete immersed in 0.5 M H2SO4, simulating industrial/microbial environment. For this, corrosion rate by linear polarisation resistance and corrosion potential as per ASTM C876-91 R99 were monitored from steel-reinforced concrete slabs admix ed with different Solanum aethiopicum leaf-extract concentrations and immersed in the acidic test-environment. Obtained test-data were subjected to statistical probability distributions for which compatibilities were tested using Kolmogorov-Smirnov goodness-of-fit statistics, as per ASTM G16-95 R04. These identified all datasets of corrosion test-data, from the steel-reinforced concrete samples, as coming from the Weibull probability distribution. Analysed results showed that Solanum aethiopicum leaf-extract reduced rebar corrosion condition from “high” to “low” corrosion risks of ASTM C876-91 R99. Also, the corrosion rate analyses identified 0.25% Solanum aethiopicum leaf-extract with optimal inhibition efficiency performance, η = 93.99%, while the other concentrations also exhibited good inhibition of steel-reinforcement corrosion in the test-environment.

Joshua Olusegun Okeniyi, Olugbenga Adeshola Omotosho, Elizabeth Toyin Okeniyi, Adebanji Samuel Ogbiye

Artificial Neural Network Modeling to Predict Hot Deformation Behavior of Zn-Al Alloy

Hot compression of the ZnCu2A110 alloy was conducted on a Gleeble-3800D thermo-mechanical simulator in the temperature range of 150–330 ℃ and strain rate of 0.01–10 s−1. Base on the experimental results, An Artificial Neural Network (ANN) with double hidden layers composing of 10 neurons and 15 neurons were employed to simulate the flow behavior. The inputs of the model are temperature, strain and strain rate. The output of the model is the flow stress. As a result, the minimum relative error is 0.01%, the maximum relative error is 2.25%, and error majority concentrate within 0.81%, Mean Absolute Percentage Error (MAPE) is 0.0101, error is very small. The results indicate that the trained ANN model is a robust tool to predict the high temperature flow behavior of ZnCu2A110 alloy

Yingli Liu, Jiancheng Yin, Ying Jiang, Yi Zhong

Behavior of Tire Derived Pre-Functionalized Carbon Black for Uranium Adsorption

Extracting uranium from the solution phase has been a challenge as very few sorbents present high adsorption efficiency. A novel adsorbent in the form of Recycled Tire Carbon Black (RTCB), derived from pyrolysis of used tires, has shown promising results in adsorbing uranium from solution phase better than other functionalized carbon materials. The RTCB has been presented as a cheap and effective sorbent whose properties don’t need to be altered to obtain nearly 97% adsorption and 99% elution using 0.15M HCl. Kinetic tests were performed to understand the adsorption rates. Langmuir isotherm model estimated that the adsorption capacity was ∼45.45 mg U/g RTCB at 80 °C with enhanced adsorption kinetics predicted by first order rate laws. In addition, the RTCB demonstrated better adsorption performance at lower pH. Characterization preformed using BET, illustrated that the surface area of the RTCB was 57 m2/g while FTIR confirmed the presence of thiol (R-S-H) functional group on the surface.

Travis Willhard, Dhiman Bhattacharyya, Mano Misra

Effect of Temperature on the Mechanical Behaviour of Ni-Ti Shape Memory Sheets

In this research the shape memory effect of commercial NiTi sheets has been investigated. Four commercial SMA elements have been characterized. Tensile tests (load-unload cycles) have been performed at various constant temperatures (from room temperature up to 60 °C). Stress-strain curves have been analyzed and discussed in order to quantify the shape-recovery which has been found higher at increasing testing temperature. A study on the energy dissipation on each cycle has been carried out too and the energy absorption on the whole load-unload cycle has been found higher as the temperature increases.

Girolamo Costanza, Maria Elisa Tata, Riccardo Libertini

Evaluation of Forged Aluminum Matrix Composites Reinforced with Carbon Nanotubes (CNTs) Fabricated by Composite Gas Generator (CGG) Process

In this study, aluminum based metal matrix composites(ALMCs) with multi-walled carbon nanotubes(CNTs) as reinforcement was produced by a recently developed composite gas generator(CGG) process. Furthermore, the liquid composites with well dispersed CNTs was forged to the slug shape part by the melt forging process, followed by heat treatment with several holding times, and microstructures and mechanical properties of forged products also were evaluated.Results shown that mechanical properties were enhanced compared to those of products without reinforcements.

Youngsek Yang, Myeonghak Kang, Geunwoo Lee

Gamma and Neutron Shielding Behavior of Spark Plasma Sintered Boron Carbide-Tungsten Based Composites

In this study gamma and neutron attenuation properties of boron carbide-tungsten (B4C-W) based composites were investigated. B4C-W based composites were produced by spark plasma sintering (SPS) method. W additions were 5%, 10%, and 15% by volume. Samples with theoretical densities were obtained. Occurance of W2B5 phase with a reaction between B4C and W particles were observed with XRD and SEM investigations. The materials were subjected to gamma and neutron sources. Cs-137 and Co-60 gamma radioisotopes were used as gamma, and Pu-Be Neutron Howitzer was used as neutron source. Linear and mass attenuation coefficients of the composites were carried out for gamma sources by using gamma transmission technique. Furthermore, total macroscopic cross-sections of the samples were determined for Pu-Be neutrons. In conclusion, increasing W ratio in the B4C-W system causes higher gamma attenuation behavior for gamma sources, but the macroscopic cross-sections of the B4C-W composites decrease by increasing W concentration.

Salih Cagri Ozer, Bulent Buyuk, A. Beril Tugrul, Servet Turan, Onuralp Yucel, Gultekin Goller, Filiz Cinar Sahin

Image Analysis Investigating Porous Structures of Carbon Cathodes Materials and Melts Penetration

During aluminum electrolysis, the cryolitic melts will penetrate into the carbon cathode block through porous structure. Na generated from the cryolitic melts will lead cathode expansion and deterioration. This work is aimed to give a better understanding of the relationship between the pore structure and the cryolitic melts penetration. Image analysis was applied to characterize the porous structures of the virgin cathode. Penetration experiments with carbon cathode materials were carried out and the penetrated melts distribution in the cathode samples were analyzed by SEM-EDS. The quantitative information of porous structures shows 50–80% pores in cathode external areas filled by melts after 180 min electrolysis tests. Most of melts penetrated into the narrow open pores. Selective mechanism of the melts penetration into pores was discussed. The information obtained could be useful for improving control of the cathode quality through quantitative image analysis.

Xiang Li, Jilai Xue, Jun Zhu, Shihao Song

Inhibition of Stainless Steel Corrosion in 0.5 M H2SO4 in the Presence of C6H5NH2

Inhibition of stainless steel corrosion in 0.5 M H2SO4 by C6H5NH2 (Aniline) at different temperatures was experimentally studied in this paper. Corrosion rate measurements at 28°C, 45°C and 60°C were taken through linear sweep voltametry and utilised for modelling inhibition efficiency and thermodynamic properties in the acidic solution containing different concentrations of the organic chemical. Results showed that inhibition of stainless steel in 0.5 M H2SO4 increased with increasing temperature for most of the different concentrations of C6H5NH2 employed. Optimal inhibition efficiency ranged from η = 26.49% by 0.043 M C6H5NH2 at 28°C, through η = 88.99% by 0.021 M C6H5NH2 at 45°C up to η = 96.68% by 0.043 M C6H5NH2 at 60°C. Also, thermodynamic property analyses showed that apparent activating energy decreases from the uninhibited, 0 M C6H5NH2, to the optimally inhibiting 0.043 M C6H5NH2 containing medium, which suggests C6H5NH2 adsorption drives the inhibition effects observed.

Olugbenga Adeshola Omotosho, Joshua Olusegun Okeniyi, Emmanuel Izuchukwu Obi, Oluwatobi Oluwasegun Sonoiki, Segun Isaac Oladipupo, Timi Moses Oshin

Micro-Truncated Cone Arrays for Light Extraction of Organic Light-Emitting Diodes

In this paper, we combined photolithography, polydimethylsiloxane (PDMS) molding, and UV-forming techniques to fabricate micro-truncated cone arrays. The taper angle of micro-truncated cone arrays was adjusted by changing softbake parameters during photography of photoresist. The fill factor of micro-truncated cone arrays was altered by varying the gap distance between two neighboring cones. In addition, the influences of taper angle and fill factor of micro-truncated cone arrays on efficiency improvement and optical properties of a blue light organic light-emitting diode (OLED) were investigated. The optical properties include spectral shift, CIE coordinates, and viewing-angle-dependent luminance. Experimental results showed that the efficiency of the OLED increased with increasing the fill factor, but decreased with the taper angle of micro-truncated cone arrays. The efficiency of the OLED could be increased up to 42% by attaching the micro-truncated cone array having a fill factor and a taper angle of 94% and 72°, respectively.

Wei-Chu Sun, Ben Hsu, Mao-Kuo Wei

Mould Filling Ability Characterisation of SIMA Produced 6063 Alloy

Metallic materials are shaped with various methods. In last 25 years, it has been found that alloys can be shaped in the solid-liquid phase region. There are several ways to produce such materials for example magnetic stirring, mechanical stirring etc. One of them involves the heating of extruded alloy above the solidus temperature which is called Strain Induced Melt Activated (SIMA) method. Heavily cold work alloy starts to recrystallize; spherical grains form and liquid surround these grains. In this way, viscosity is decreased and the material can be shaped very easily under pressure. In this work, AA6063 extruded alloy was used to produce a (shaped sample). Different temperatures, holding times and pressures were selected to characterize the mould filling ability of the alloy. Micro structural examinations and hardness tests were carried out.

Ömer Vardar, Izzettin Ergün, Çağlar Yüksel, Eray Erzi, Derya Dispinar

One-Step Preparation of TiB2-C Composite by DC Arc Furnace

Previous approaches to prepare bulk TiB2-C composite is sintering the TiB2 powder mixed with the C component, so that lead to a series of problems, due to the bad sintering properties. This paper discribes a one-step method of preparing the TiB2-C composite, especially for using as inert cathode in electrolytic aluminum, from the raw materials of TiO2, B2O3 and petroleum coke, by a dc arc furnance. The rapid and high-temperature heating process provided by the arc furnance leads to the carbothermal reaction to prepare TiB2, and the overdosed carbon is included in TiB2 matrix. The XRD(X-Ray Diffraction), SEM(Scanning Electron Microscope), and chemical component analysis are used in the testing part, and the one-step process of preparing bulk TiB2-C composite is studied.

Kuanhe Li, Shuchen Sun, Xiaoxiao Huang, Shuaidan Lu, Xiaoping Zhu, Ganfeng Tu

Si and SiCu Three Dimensional Sculptured Films as Negative Electrodes for Rechargeable Lithium Ion Batteries

Three dimensional sculptured Si films with (10 %at.) and without Cu contents have been fabricated by an ion-assisted glancing angle co-deposition technique. Once the morphological and structural differences depending on Cu contents of the films have been evaluated, their uses as anodes in lithium ion batteries have been also discussed. The morphological analyses demonstrate that Cu presence improves nano ordering and the homogenity along the nano sculptured structure. The galvanostatic tests show that the film without Cu fails quickly, but the one with 10%at. Cu content delivers 800 mAh g−1 with 99% coulombic efficiency after 100th cycles. It is believed that the composite electrode has a better electrochemical performance because Cu plays a crucial role in holding the electrode together, buffering the mechanical resistance and enabling faster electron transfer.

B. Deniz Polat, Ozgul Keles

Thickness Effect on the Three-Dimensional Sculptured SiCu Thin Films Used as Negative Electrodes in Lithium Ion Batteries

SiCu (10 %at. Cu) composite three dimensional sculptured films with different thicknesses have been fabricated by an ion-assisted glancing angle co-deposition technique. The films have been evaluated as anodes considering morphological and structural differences depending on the different evaporation durations. The galvanostatic tests show that after 50th cycles the thin film delivers 2124 mAh g−1, but the thick electrode performs 685 mAh g−1 as dicharge capacities. It is believed that the thin film electrode has a better electrochemical performance because increase in process time causes deformation in the helice’s morphology, increase in ohmic resistance and generation of more stress in the electrode.

B. Deniz Polat, Ceren Yagsi, Ozgul Keles

ICME Infrastructure Development for Accelerated Materials Design: Data Repositories, Informatics, and Computational Tools

An Integrated Model for Prediction of Yield Stress in Al-7Si-Mg Cast Alloys

The desired mechanical properties of Al-7Si-Mg cast alloys can be achieved by a corresponding processing process, and are extensively used in automotive and aerospace industries. The prediction of the microstructure controlling mechanical properties is meaningful in order to further modify the properties of castings. In present research, a microstructure-strength relation based model was developed to predict the yield stress of Al-7Si-Mg cast alloys. The as-cast microstructure was simulated by cellular automaton model and its effect on yield stress was considered. Based on the general framework proposed by Kampmann and Wagner, a multi-component precipitation model involving nucleation, growth and coarsening of precipitates, as well as a strengthening model were developed. Applications of these models to an engine block casting were carried out to predict the as-cast microstructure as well as the final yield stress, and the predictions were verified with experimental results.

Rui Chen, Qingyan Xu, Zhiyuan Xia, Huiting Guo, Qinfang Wu, Baicheng Liu

Experiences with ICME Information Infrastructures for Applying Materials Models in Sequence to Give Accurate Macroscopic Property Prediction

This paper draws on findings from the Material Data Management Consortium. The consortium, now in its 15th year, enables leading engineering enterprises (including among others GE, Boeing, Honeywell, Lockheed Martin, and NASA) to collaborate on best practice approaches to managing and applying critical materials information and technology with a key focus on traceable workflows for simulation and multi-scale modelling of materials, their processing and the resulting components.A key emphasis has been on verification and validation of macroscopic materials properties generated through sequentially-applied materials models; from ab-initio codes or models of microscopic unit cells through calculations at various length scales up to macroscopic properties. An example of this integration technology is described, using the MAC/GMC micromechanics code from NASA Glenn Research Center. Focus is given to the traceability of the simulated data and capture of sufficient metadata to ensure that the simulations can be recreated in future. The traditional method for understanding the effects of these different factors on materials innovation follows a set pattern where advantageous properties are pursued, iterating between process and structure while measuring the appropriate property. Progress relies on extensive and expensive physical testing campaigns, which generate vast quantities of highly complex data. There are hundreds of possible test types within materials engineering, all generating data of differing types, complexity, and different formats.

Will Marsden, David Cebon, Steven Arnold, Brett Bednarcyk, Nic Austin, Igor Terentjev

D2C — Converting and Compressing Discrete Dislocation Microstructure Data

Appropriate methods to describe materials microstructure are essential for connecting different simulation methods as well as experiments. Focusing on dislocations — the carrier of plastic deformation — we show how continuous field descriptions can be used to represent dislocation microstructure. These fields may be used as input for continuum simulations or for their validation, they allow the comparison of different discrete dislocation dynamics (DDD) implementations, and they are a means of “compressing” the data resulting from DDD simulations. We give an overview of the design choices for D2C, a Python software package designed to convert data from DDD simulations to continuous continuum dislocation dynamics (CDD) fields. The theory beneath each step of this conversion process is outlined.

D. Steinberger, M. Leimberger, S. Sandfeld

Material Behavior Characterization via Multi-Directional Deformation of Sheet Metal

Determination of Bending Limit Curves for Aluminium Alloy AA6014-T4: An Experimental Approach

The conventional forming limit curves as proposed by Keeler and Goodwin fail to evaluate formability in case of bending and hemming operations. This is due to the different failure mechanisms involved in biaxial forming and bending/hemming operations. To overcome this difficulty, concept of bending limit curve has been introduced. This work presents an experimental approach to determine the BLC for aluminium alloy AA6014-T4. AA6014-T4 was selected as the workpiece due to its extensive application in outer panels of car bodies. The bending samples were printed with speckle pattern and measurement of bending strain was carried out with the help of GOM Aramis software. The three point bend test was conducted with two punch radii of 0.4 mm and 2 mm to study the effect of punch radius on bending limit strains. The complete formability picture was obtained by plotting combined forming limit and bending limit curves.

Ipsita Madhumita Das, Krishna Kumar Saxena, Jyoti Mukhopadhyay

135° Clock Rolling: An Approach to Improve the Microstructure and Texture of Tantalum Used for Sputtering Target

An efficient approach, 135° clock rolling, to improve the microstructure and texture of tantalum (Ta) was presented in this paper. The Ta plates were processed by unidirectional (UR) and clock rolling (CR), respectively. Compared with UR, the novel CR caused a continuous change of strain paths and consequently activated slip systems from multiple directions. After cold rolling, the microstructure and texture were investigated by the optical microscopy (OM), X-ray diffraction (XRD), electron channel contrast imaging (ECCI) and electron back-scattered diffraction (EBSD) techniques. Results showed that 135°clock rolling had positive effects on weakening the texture gradients and homogenizing the deformation microstructure, thus resulting in a favorable annealing behavior and eventually improving the sputtering performance of Ta target.

Haiyang Fan, Shifeng Liu, Chao Deng

Material Design Approaches and Experiences IV

Evolution Law of Grain Size of High Alloy Gear Steel in Hot Deformation

The change rules of deformation parameters such as temperature, strain and strain rate at different zones of forgings are very complex in the forging process of high alloy chromium-cobalt gear steel, and the deformation parameters have great influence on grain sizes. In this paper, recrystallization model for the steel was established with the material characteristic parameters obtained from the Gleeble isothermal compression test, influencing factors were analyzed based on the model. The results indicate that recrystallization grain size increases with increasing temperature and decreasing strain and strain rate, and the effect of temperature is more obvious than the other two. The average grain sizes are between 27.7μm∼40μm at 1040°C of forging temperature, grain size degree 6∼6.5, meeting the product requirements.

Tang Hai-yan, Yang Mao-sheng, Meng Wen-jia, Li Jing-she

Experimental Investigation of the Sm-Rich Side in Sm-Zr System

The information of phase diagram for the Sm-Zr system is deficient. A diffusion couple and two alloys in Sm-rich side of Sm-Zr system were prepared. The phase equilibrium in the alloys at 800 and 900 °C were determined by scanning electron microscopy, equipped with energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction(XRD). The results show that a peritectic reaction exists in the Sm-rich end. The solubility of Sm in (Zr) was detected to be about 2.4 at.% at 800°C and 2.7 at.% at 900 °C. The solubility of Zr in (Sm) is negligible. No binary compound is detected in the XRD patterns in all samples.

Tian Yin, Shuqiang Zhang, Zhihong Zhang, Jieyu Zhang

Materials and Fuels for the Current and Advanced Nuclear Reactors V

Fabrication and Qualification of Small Scale Irradiation Experiments in Support of the Accident Tolerant Fuels Program

The Accident Tolerant Fuels (ATF) program aims to develop next generation Light Water Reactor (LWR) fuels with improved performance, reliability, and safety. The program has developed a roadmap to support the insertion of demonstration lead fuel rods (LFRs) or lead fuel assemblies (LFAs) into a commercial LWR by the end of FY 2022. In order to achieve this goal, novel fuel compositions and cladding materials are being assembled for drop-in irradiation experiments that afford prioritization of candidate concepts within the ATF Program. Development of fabrication methodology and qualification techniques for small-scale irradiation test samples is reported.

Connor Woolum, Kip Archibald, Glenn Moore, Steven Galbraith

Development of Engineering Parameters for Low Pressure Diffusion Bonds of 316 SS Tube-to-Tube Sheet Joints for FHR Heat Exchangers

Diffusion bonding is a solid-state welding technique to join metallic and non-metallic materials. Due to geometrical considerations, fabrication and possible materials choices diffusion bonding was chosen here for tube-to-tube sheet joints of large coil wound heat exchangers for Fluoride salt cooled High temperature Reactors (FHRs). In this work the processing parameters for these critical nuclear component manufactured out of 316l stainless steel are presented and the bonded areas are investigated using optical microscopy (OM) and scanning electron microscopy (SEM). In addition mechanical tests were conducted (pull out testing) to evaluate if these joints are sufficiently bound to guarantee a safe operation of the device. The detailed joining parameters are reported and recommendations for future fabrications with the physical restrictions of a large heat exchanger are made.

Nils Haneklaus, Rony Reuven, Cristian Cionea, Peter Hosemann, Per F. Peterson

Mechanical Behavior at the Nanoscale III

The Microstructure and Mechanical Properties of Nanometer Al2O3/Cu Composite Fabricated by Internal Oxidation

The fabrication of the copper matrix composites strengthened with dispersal nanometer Al2O3 is investigated. The investigation result shows that the atomized Cu-Al alloys powders mixed with Cu2O oxidant powders were internally oxidized at 1173K for an hour in nitrogen atmosphere. X-ray and EDS analysis indicates that the particles formed during internal oxidation consist of a large amount of CuAlO2 and a certain amount of α-Al2O3. After hydrogen reduction at 1173K for an hour, the particles turn to be α-Al2O3. TEM observation shows that the obtained α-Al2O3 particles are uniformly distributed in copper grain, and the mean size of these particles is about 10 nm. As compared with the composite by a previous sintering, the main properties of the composite with 50% cold deformation are better.

Lei Guo, Shuqiang Guo, Shuai Ma, Jie Liu, Weizhong Ding

Nanostructured Materials for Nuclear Applications

The Roles of Oxide Interfaces and Grain Boundaries in Helium Management in Nano-Structure Ferritic Alloys: A First Principles Study

We report a theoretical study for assessing the possible roles of oxide interfaces in managing helium in nano-structured ferritic alloys (NFAs). Various candidate structures of the ferrite/Y2Ti2O7 interfaces are constructed and the associated energies are carefully evaluated. The calculated interface phase diagram predicts the interfaces to be Y/Ti-rich, for the wide temperature range of interest. Vacancies and helium both segregate to the interfaces, in preference to grain boundaries. Combined with our previous results on bulk-phase Y2Ti2O7, the profound implication of helium management in NFAs is discussed.

Y. Jiang, L.-T. Yang, J. Xu, G. R. Odette, Y. Wu, T. Yamamoto, Z.-J. Zhou, Z. Lu

Phase Transformations and Microstructural Evolution

The Stability of the Moving Boundary in Spherical and Planar Geometries and Its Relation to Nucleation and Growth

Coupled heat and mass diffusion equations are set up and solved for various Stefan numbers. A stability criterion is developed for the moving interface. The general MBP is of importance in many fields, particularly in directional solidification. The analysis is applied to the homogenous nucleation and growth of a spherical particle. Traditional analyses have relied on energy balances between surface and volumetric energy. An exact solution is analyzed for appropriate boundary conditions here. The present derivation presents unpublished analyses using perturbation and consideration of the unknown moving boundary of the nucleating particle. Only certain solutions for the MBP are known and it is difficult to find solutions for the general case due to the extreme non-linear nature of the problem because of discontinuous material properties across the liquid and solid regions, and the unknown position of the liquid solid phase boundary. These concepts are applied to nucleation and phase field theory for homogenous nucleation with application to amorphous alloy formation.

Rahul Basu

Effect of Pulse Magnetic Field on Isothermal Bainitic Transformation Process in Cr5 Steel

In order to investigate the effect of pulse magnetic field on isothermal bainitic microstructure and performance of Cr5 steel, pulse high magnetic field with 1.5T was exerted during isothermal bainitic transformation, continuous cooling + isothermal bainitic transformation and austenitizing + continuous cooling + isothermal bainitic transformation process, respectively. Results showed that, compared with normal isothermal bainitic transformation with the same technology, applying pulse magnetic field during the isothermal bainitic transformation can obviously promote bainitic transformation, the volume fraction of bainite increased by 4.2%, the volume fraction of retained austenite is reduced by 1.7%, and the hardness of Cr5 steel was reduced by 3 HRC.

Wenming Nan, Daping Zhang, Lijuan Li, Qingchun Li, Qijie Zhai

Corrosion Effects on Mechanical Properties of Sensitized AA5083-H116

The impact of sensitization levels resulting from exposure to a temperature of 150°C on AA5083-H116 mechanical properties was investigated through accelerated corrosion. Optical microscopy was performed to examine microstructure damage morphologies dependent upon β grain boundary coverage evolution and surface orientations. Corrosion in 0.6 M NaCl solution at −0.77 V from 3–48 hours led to parallel damage on exposed LT surfaces and perpendicular attack on exposed LS surfaces. After 48 hours of corrosion, a degree of sensitization (DoS) of 61 mg/cm2 was observed; an intergranular corrosion (IGC) damage depth of 184 μm occurred on the LT surface and IGC damage depth of 720 μm occurred on the LS surface. At a DoS of 66 mg/cm2, yield and ultimate tensile strengths decreased by 19% and 5%, respectively, when compared to the as-received state, while LT surface corrosion after 120 hours reduced strengths by 26% and 14%, respectively, from the as-received state.

Robert J. Mills, Brian Y. Lattimer, Scott W. Case

The Effect of Initial Microstructure on the Mechanical Properties of Bi-lamellar Ti-6Al-4V

Bi-lamellar microstructure can be realized by intercritical annealing followed by rapid cooling of lamellar microstructure in titanium alloys. The mechanical properties can be improved by the introduction of fine secondary αlamellars in-between coarse α lamellars in the bi-lamellar structures. In this study, the influence of initial microstructures, including martensite microstructure and lamellar microstructure, on the resulting bi-lamellar microstructures as well as its mechanical properties was systematically investigated. Colony size was significantly reduced by starting from martensite microstructure compared with that started from lamellar microstructure. Consequently, both yield strength and uniform elongation of bi-lamellar microstructure were improved. The improvement was explained by decreased slip length based on “effective” grain size of two different scales, i.e., α lamellar thickness and α colony size. In addition, the phenomenon of crack propagation through secondary α lamellar with certain orientation is discussed.

Yan Chong, Nobuhiro Tsuji

Some Steps towards Modelling of Dislocation Assisted Rafting: A Coupled 2D Phase Field — Continuum Dislocation Dynamics Approach

The interaction between edge dislocations and γ′ precipitates as in nickel-based super-alloys is studied by coupling a phase field model and a 2D continuum dislocation dynamic model. Various stresses, which serve as communicator between dislocations and precipitates, are calculated by an eigenstrain method for both the γ/γ′ misfit and the dislocations. Our simulations show how edge dislocations tend to move to and pile up at specific γ/γ′ interfaces. The growth of γ′ is inhibited at the interface where dislocations are piling up, due to the reduction of elastic energy. The potential of our coupled model for simultaneous microstructure patterning and mechanical property prediction is discussed.

Ronghai Wu, Stefan Sandfeld

Effect of Heating Types on the Undercooled Solidification Microstructure of Co76Sn24 Eutectic Alloy

Melt processing is implemented on Co76Sn24 eutectic alloy through different heating types including induction heating and resistance heating to prepare samples with same undercooling. Effect of heating types on the undercooled solidification microstructure has been studied by observation and analysis of the microstructure. Results indicate that induction heating makes the primary phase refined, the volume fraction of primary phase increased and anomalous eutectic easier to form when compared with resistance heating under same undercooling.

Tong Guo, Jun Wang, Xiaoxing Qiu, HongChao Kou, Jinshan Li

Mechanical Properties of 5000 Series Aluminum Alloys Following Fire Exposure

An experimental study was performed comparing changes in microstructure and mechanical properties of six different 5000 series alloys following a simulated fire exposure. To simulate the fire exposure, specimens were subjected to a constant heating rate of 25 °C /min (up to 500 °C) and then water quenched. Quasi-static tensile tests were conducted to quantify yield strength. Additionally, grain evolution was examined by optical microscopy for each alloy. The 5000 series alloys with different tempers resulted in residual strengths between 85 and 157 MPa following the fire exposure. Most alloys exhibited recovery between 100 °C to 280 °C followed by recrystallization between 300 °C to 340 °C. However, the 5456-H116 alloy, which has the highest magnesium content, maintained 60% of room temperature yield strength. This alloy underwent recovery but did not have a clear recrystallization, as apparent in both the micrographs and mechanical testing.

Jillian C. Free, Patrick T. Summers, Brian Y. Lattimer, Scott W. Case

Effect of Concurrent Microstructure Evolution and Hydrogen Level on Flow Behavior of Near Alpha Ti-Alloy

Separate compression samples of VT20 Ti-alloy Ti-5.9Al-2.1Zr-1.6V-1.4Mo (wt%), charged with 0, 0.15 and 0.36 wt%H, were deformed to true strain of 0.70 at a strain rates of 1×10−3 and 1×10−1 s−1 at test temperatures of 600 and 850 °C. H charging led to the varying microstructures ranging from equiaxed to lamellar ones depending on H level. In the course of deformation, their occurred refinement of microstructures with reduced interlamellar spacing depending on the test conditions. The contributions of these sources to microstructure evolution and flow properties were examined in an attempt to explore some correlation between them. An attempt is made to understand the effect of H present on the microstructure and flow properties to account for the variations in the parameters of the constitutive relationship.

Jagadeesh Babu, B. P. Kashyap, N. Prabhu, R. Kapoor, R. N. Singh, Bhupendra K. Kumawat, J. K. Chakravartty

Using Temporary Hydride Formation in Metastable Beta Titanium Alloys to Improve the Microstrcture

Hydrogen can be used as a temporary alloying element during the heat treatment, often referred to as Thermohydrogen Treatment (THT), in order to improve the mechanical properties of titanium alloys by means of microstructure modification being unobtainable by conventional heat treatment. THT is based on the changes of the stability and transformation kinetics of phases as well as on the formation of hydrogen-induced phases. The volume effects associated with hydride formation lead to local matrix deformation accompanied by an increase in the dislocation density. It is shown in this contribution that hydride formation accompanied by a hydrogen-induced redistribution of alloying elements and subsequent complete hydride dissolution can be used to establish a fine microstructure via hydride-induced recrystallization (Ti 10-V-2Fe-3Al) and a homogeneous formation of alpha nuclei indirectly via hydride precursors (Ti 3Al-8V-6Cr-4Mo-4Zr).

Hans-Jürgen Christ, Vitali Macin

Numerical Simulation of Solidification Microstructure with Active Fiber Cooling for Making Fiber-Reinforced Aluminum Matrix Composites

Solidification process is very important for making fiber reinforced aluminum matrix composites. Some recent studies have used cooling through reinforcing carbon fibers to obtain better control over the solidification microstructure in the post pressure infiltration process. The present work is focused on studying the effect of active cooling fiber on temperature, thermal stresses and microstructure of aluminum matrix composites. The predicted results show that the temperature gradients of both the matrix and the carbon fiber vary continuously before loading the stress field, while the temperature gradient between the fiber and Al2014 melt become steeper as a cliff after loading the stress field (when Al2014 melt solidified completely). The predicted results of temperature contour agree well with the result of references. The microstructure simulation results shows that grains grow along the opposite direction of heat flow, and form the finer equiaxed grains away from the cold end.

Zhiliang Yang, Bo Wang, Shupei Liu, Jie Ma, Wanping Pan, Shuai Feng, Liang Bai, Jieyu Zhang

Assessment of Tribological Properties of Cast and Forged Ti-6Al-7Nb and Ti-6Al-4V Alloys for Dental Applications

Thermal oxidation treatment is an easy and environment friendly technique that can be used to harden the surface of titanium alloys, and hence improve the poor tribological properties of these materials. The aim of the present research was to evaluate the tribological behavior of cast and forged Ti6Al7Nb and Ti6Al4V implants after different thermal oxidation treatments. A significant increase in surface hardness of the two alloys was achieved due to the formation of a hard oxide layer and oxygen diffusion zone beneath it. The oxygen diffusion zone, which was generated at 900 °C, showed the best wear resistance in case of Ti6Al4V alloy. On the other side, no remarkable enhancement was observed in the Ti6Al7Nb alloy even at 1100 °C, regardless of the improved surface hardness. In addition, the development of alpha case in the cast samples was different from the forged ones. The widmanstätten microstructure of the cast samples showed thinner alpha case compared to the equiaxed structure of the forged samples in both alloys.

Ahmed Zaki, Shimaa El-Hadad, Waleed Khalifa

Phase Transformations in Multi-component Systems: An MPMD Symposium Honoring Gary R. Purdy

Solid State Reaction of Nd2Fe14B and Carbon

X-ray diffraction (XRD), scanning electron microscopy (SEM), inductive-coupled plasma spectroscopy (ICP), oxygen analyzer were used to investigate the solid state reaction of Nd2Fe14B powders with carbon. The experiment results revealed that Nd-rich phase (FCC-NdO) was formed after sintering when the samples contain oxygen (1 percent). With the carbon content of Nd-rich phase increasing, the Nd-rich phase changed from FCC-NdO phase to h-Nd2O3 phase. And the phase evolution of Nd-rich phase was sensitive to the carbon concentration as well as the sintering time. When the oxygen free samples sintering over 1100 °C, the phase evolution of iron was sensitive to the sintering temperature. With the temperature increased to 1300 °C, the Nd-rich compounds (NdFeC compounds) decreased and the NdC2 increased.

Jie Liu, Shuqiang Guo, Yuyang Bian, Lei Guo, Lan Jiang, Man Zhang, Shuai Ma, Weizhong Ding

Powder Metallurgy of Light Metals

Production of Titanium Hydride Powder by Leaching of Aluminum and Silicon Impurities from Reduced Upgraded Titania Slag for Low Cost Titanium Production

Titanium alloys are in great demand in engineering applications that require better mechanical properties at a lower weight than steel, but high costs of titanium alloys have restricted their use in day to day applications. A novel low cost route for titanium powder production has been proposed recently, which involves reducing and purifying upgraded titania slag (UGS). The UGS is reduced with magnesium hydride in a hydrogen environment to form titanium hydride along with aluminum, iron and silicon impurities, originating in the UGS. It is crucial to remove the impurities from reduced UGS for successful implementation of this new proposed route for titanium production. This investigation is focused on removal of aluminum, and silicon impurities from the reduced UGS powder by leaching techniques in both alkaline and acidic conditions. The results indicate that proper operating conditions lead to high levels of impurity removal.

Syamantak Roy, Jaehun Cho, Nathan J. Hamilton, Amarchand Sathyapalan, Michael L. Free, Zhigang Zak Fang

Mechanical Properties and Microstructure of PM Ti-Si3N4 Discontinuous Fibre Composite

2 vol% Si3N4 fiber Ti composites were manufactured by uniaxially pressing the powders and subjecting the green compact to pressureless sintering at 1400°C in flowing argon. The resulting composites were >98% theoretical density. The hardness of the titanium composite was measured at HBW 401 compared to HBW 293 for pure titanium. Microstructural analysis showed clearly defined 200–300nm diameter crystalline fibers throughout the composite with a 2–4μm reaction boundary cementing them to the titanium. Concentrations of smaller Si3N4 particles were located at the titanium grain boundaries, which may have reacted to form Ti-Si-N phases. The improved mechanical properties might be from a combination of discontinuous fiber reinforcement, nitrogen addition to the Ti matrix, and grain-boundary reinforcement.

Troy Dougherty, Ying Xu, Ainaa Hanizan

Microstructure Evolution and Mechanical Properties Investigation of Friction Stir Welded AlMg5-Al2O3 Nanocomposites

The present study has investigated the influence of friction stir welding (FSW) on the microstructure and mechanical properties of powder metallurgy processed unmilled AlMg5, AlMg5 milled with 0.3 wt. % stearic acid (SA) and milled AlMg5–0.5 vol% Al2O3 nanocomposites. FSW of unmilled AlMg5 resulted in grain refinement due to dynamic recrystallization induced by the thermo-mechanical processing, thereby increasing the stir zone yield strength (YS) and ultimate tensile strength (UTS) to 160 MPa and 326 MPa when compared to 135 MPa and 300 MPa of base metal, respectively. The friction stir AlMg5–0.5 vol% Al2O3 nanocomposite exhibited superior mechanical properties compared to almost all commercial 5xxx series of Al alloy friction stir welds. However, the friction stir welded AlMg5 milled with 0.3 wt. % SA and AlMg5–0.5 vol% Al2O3 samples showed a slight reduction in UTS values (373 MPa and 401 MPa) compared to 401 MPa and 483 MPa of respective base metal values.

N. Kishore Babu, Kaspar Kallip, Marc Leparoux, Khaled A. AlOgab, G. M. Reddy, M. K. Talari

Titanium Foam for Cancellous Bone Implant Prepared by Space Holder Technique

Open-cell titanium(Ti) foams with 75.5% porosity were manufactured by powder metallurgy route using acicular carbamide particles as space holder. The TG and DSC curves of carbamide were measured to optimize the heat treatment during carbamide removal. X-ray diffraction studies of carbamide before and after removed to ensure that the foams produced featured no contamination. The compressive strength and Young’s modulus of Ti foams were 11.1 MPa and 0.32 GPa, respectively. This kind of open-cell the foam is expected to be a potential substitute biomaterial for cancellous bone, due to its mechanical properties well match that of cancellous bone.

Xiao Jian, Cui Hao, Qiu Guibao, Yang Yang

Recent Developments in Biological, Structural and Functional Thin Films and Coatings

Thin Films and Coatings for Absorptive Removal of Antimicrobials, Antibiotics, and other Pharmaceuticals

The US EPA regards “emerging pollutants” as new unregulated chemicals which impact the environment and human health. Many chemicals such as analgesics, anti-inflammatories, beta-blockers, antibiotics, and antimicrobials are not being effectively removed in water treatment. Triclosan, a ubiquitous antimicrobial that is widely used in antibacterial products and in clinical situations is of growing concern as it has been found to degrade human health with potentially devastating promotion of cancer and autoimmune diseases. In this study we are exploring the removal of triclosan using molecular modeling and absorptive/adsorption experiments on modified clays monitored by Tandem Liquid Chromatography — Mass Spectrometry (LCMS). Thin films and coatings offer the opportunity to build complex structures, save materials and engineer hybrid systems. Manual coating (brushing, dipping and air spraying) as well as 3D printing has been explored.

David Cocke, Andrew Gomes, Saiful Islam, Gary Beall

Effect of Post-Heat Treatment on the Electrochemical Performance of Sandwich Structured Cu/Sn/Cu Electrode

In this work, we have produced Cu/Sn/Cu sandwich structured film by electrodeposition method, to be used as a negative electrode for rechargeable lithium ion battery. To promote the interaction between Cu/Sn/Cu layers, an additional post-heat treatment (200°C, 48h under vacuum atmosphere) has been applied to the coatings. The galvanostatic test results prove that morphological changes and CuxSi intermetallics formation in the film as a result of heat treatment process promote the capacity retention of the electrode. After 30 cycle, the capacities of the Cu/Sn/Cu electrodes with and without heat treatments are 230 mAh g−1, 100 mAh g−1 respectively. This demonstrates that the post-heat treatment process improves cycle performance of the electrode.

B. Bilici, B. D. Polat, O. Keles

Role of Membrane Properties on Charge Transport Across Conjugated Oligoelectrolyte Modified Phospholipid Bilayers

Microorganisms have diverse metabolic pathways that enable them to convert hard to use energy sources (e.g., waste water) into useful products such as fuels, chemicals, and electrons for power generation. In many cases, bioelectrochemical systems have the potential to monitor, control, and enhance this metabolism for bio-processing, bio-reformation of fuels, and waste mitigation but slow microbe/electrode charge transfer has limited power densities and waste mitigation rates. Recent work has demonstrated that conjugated oligoelectrolyte (COE) additives enhance the microbial fuel cell power density and waste mitigation, but it remains poorly understood how additives like the COEs interact in phospholipid membranes. Here we examine how phospholipid membrane properties such as fluidity and charge alter COE incorporation and charge transport, using techniques including cyclic voltammetry and absorption spectroscopy. These properties are found to strongly influence COE behavior and can lead to large enhancements of both COE incorporation and activity.

Justin P. Jahnke, Guillermo C. Bazan, James J. Sumner

The Investigation on the Intermetallic Layer of Hot Dipping Al-10Si Alloy with 22MnB5 and DC51 Substrate

Hot-dipping Al-Si coating of 22MnB5 steel and DC51 steel were done in molten Al-Si bath with about 10%Si for different dipping time ranging from 3 to 300 seconds, at the temperature of 660°C, 680°C and 700°C. To study the influence of different matrix, temperature and dipping time on the intermetallic layer, the microstructure of the intermetallic layer was observed by scanning electron microscope(SEM) with energy dispersive spectroscopy(EDS). The results show that the both intermetallic layers are mainly composed of Fe2Al5 and Al9Fe2Si210-Al9Fe4Si3 was found near the boundary of Fe2Al5 and Al-Fe-Si intermetallic layer when the dipping time up to 300s. It also shows that the growth rate of interfacial layer on the 22MnB5 substrate is bigger than the intermetallic layer on DC51 steel at the same temperature (660°C, 700°C) except 680°C in a certain time range.

Weidong Hu, Wende Dan, Wangjun Peng, Guangxin Wu, Qing Du, Jieyu Zhang

The Wetting Behavior of Fe-Si and Fe-Mn Alloy with Al-10%Si Coating

High-strength steel possesses excellent strength, toughness, wear resistance and weld-ability and therefore, are widely used in various fields. Because the high strength steel contains highly content of Mn and Si, they always lead to quality problem for the process of hot-dip aluminum coating. In this work, we applied improved sessile drop method, selected some characteristic systems to measure the change in contact angle and diameter of Al-10%Si droplets wetting on a quality of Mn (0wt%, 0.5 wt%, 1.5wt%, 2.5wt%) and Si (0wt%, 0.5wt%, 1.5wt% 2.5wt%). Then the microstructure and composition of interfacial layer are analyzed by SEM/EDS, the phase composition is analyzed by XRD. The results showed that the contact angle is increasing with the contents of Si increasing. However, the contact angle is decreasing with the contents of Mn increasing.

Wende Dan, Guangxin Wu, Bo Zhang, Qing Du, Wangjun Peng, Weidong Hu, Jieyu Zhang

Refractory Metals 2016

Improving the Performance of Nb-Silicide Based Refractory Alloys Through a Novel Cold Crucible Directional Solidification

Nb-silicide alloy with composition of Nb-22Ti-16Si-3Cr-3Al-2Hf (at.%) was directionally solidified into square ingots at different processing parameters through a novel cold crucible directional solidification technology. The effect of directionally solidified processing parameters, such as heat power and withdrawal rate, on the microstructure and mechanical properties was analyzed. Results show that the directional structure composed of coupled growth of (Nb,Ti)ss/(Nb,Ti)5Si3 composite can exhibit good tension performance at 1250°C.

Hongsheng Ding, Kun He, Shiqiu Liu, Yongwang Kang, Jingjie Guo


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