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About this book

The Magnesium Technology Symposium, the event on which this collection is based, is one of the largest yearly gatherings of magnesium specialists in the world. Papers represent all aspects of the field, ranging from primary production to applications to recycling. Moreover, papers explore everything from basic research findings to industrialization. Magnesium Technology 2020 covers a broad spectrum of current topics, including alloys and their properties; cast products and processing; wrought products and processing; forming, joining, and machining; corrosion and surface finishing; and structural applications. In addition, there is coverage of new and emerging applications.

Table of Contents

Frontmatter

Keynote Session

Frontmatter

Twin Transmission Across Grain Boundaries in Mg

Transmission of $$ \left\{ {10\bar{1}2} \right\}\left\{ {\bar{1}011} \right\} $$ mechanical twins across grain boundaries in Mg is a mechanism that can facilitate shear accomodation but also provide a path for failure via intergranular crack propagation. Until recently the twin research has focused on a 2D characterization of intragranular propagation and intergranular transmission along the forward propagation direction. Recent 3D studies of the twin domain interface reveal a faceted structure, anisotropic mobility, and a relative easiness of lateral twin propagation (as opposed to forward or normal propagation). Here we describe a study of the forward and the lateral twin transmission into neighbors applying a variety of experimental and computational characterization techniques, namely: (1) statistical EBSD analysis of twin sections; (2) 3D Phase Field and Molecular Dynamic simulations of twins propgating and reacting with grain boundaries. This study improves our understanding of the transmission mechanisms in a 3D aggregate, and helps us to develop criteria for treating twin modeling in CP simulations.

Carlos N. Tomé, Mariyappan Arul Kumar, John Graham, Khanh Dang, Yue Liu, Pengzhang Tang, Shujuan Wang, Rodney J. McCabe, Laurent Capolungo

Hierarchically Structured Ultrafine Grained Magnesium Alloys

The intrinsic low density of magnesiumMagnesium drives research towards high-performance magnesium alloysMagnesium alloy (Mg alloy). Hierarchically structured ultrafine grained magnesium alloysMagnesium alloy (Mg alloy) possess exceptional strength-ductility combination and eliminate many of the traditional drawbacks like low strength, high yield strength asymmetry, poor formabilityFormability, and limited superplasticity. In this overview presentation, friction stir processed microstructures are used as examples to discuss the microstructural paradigms that can exhibit excellent balance of mechanical propertiesMechanical properties. These show the possibilities of exceeding 500 MPa strength with good work hardeningWork hardening and >10% ductility. Use of micron-sized boron carbide (B4C) and nano-sized yttria (Y2O3) powder can simultaneously enhance modulus-strength-ductility combination. High-strength ultrafine grained magnesium alloysMagnesium alloy (Mg alloy) also show high strain rate superplasticity which can provide pathways for overcoming poor formabilityFormability. An example of friction stir additive manufacturing will be used to discuss possibilities of implementing such microstructures at component level with emerging solid-state additive manufacturing techniques.

Rajiv S. Mishra

Multistage Fatigue (MSF) Modeling of Magnesium in a Corrosion Environment

Mark F. Horstemeyer

Novel Texture Controlling of Mg Alloys

Bin Jiang, Guangsheng Huang, Jiangfeng Song, Dingfei Zhang, Fusheng Pan

Alloy Development

Frontmatter

Design of Ductile Rare-Earth-Free Magnesium Alloys

Pure Mg has low ductilityDuctility due to a transition of $$ {\langle} \varvec{c} + \varvec{a} {\rangle} $$ pyramidal dislocations to a sessile basal-oriented structure. Dilute alloying generally improves ductility. Enhancement of pyramidal cross-slip from the lower-energy pyramidal II plane to the higher-energy pyramidal I plane has been proposed as the mechanism. Here, the theoryTheory is applied to ternary and quaternary alloys of Zn, Al, Li, Ca, Mn, Sn, K, Zr, and Sr at dilute concentrations, and a wide range of compositions are predicted to have good ductility. Interestingly, while Zn alone is insufficient for achieving ductilityDuctility, its inclusion in multicomponent alloys at 0.5 at.% enables ductility at the lowest concentrations of other alloying elements. Further implications of the theoryTheory are discussed.

W. A. Curtin, Rasool Ahmad, Binglun Yin, Zhaoxuan Wu

Microstructure Evolution and Precipitation Strengthening in Ca-Containing Mg-Rare Earth Alloys

The significant precipitationPrecipitation strengthening during aging provides Mg-rare earthRare earth (RE) alloys with exceptional strength. The low density and reasonable cost of Ca could favor Mg alloysMagnesium alloy (Mg alloy) for commercial use with improved properties. In order to investigate the potential interaction effect of Ca for improving the aging response and strength of Mg–RE alloys, this study was performed. 0.5 wt% and 1.0 wt% Ca were added to the ternary alloyAlloy Mg–2 wt%Nd–4 wt%Y. The microstructures of different processing conditions were examined by a series of experimental characterization techniques. The microstructureMicrostructure evolution and phase transformations were also calculated by commercial CALPHADCALculation of PHAse Diagrams (CALPHAD) software. Vickers hardness tests were performed to characterize the aging response of the quaternary Mg–2 wt%Nd–4 wt%Y–0.5 wt%Ca alloyAlloy . Current results showed that 0.5 wt% Ca addition accelerated the peak aging, as compared to the previously studied ternary Mg–Nd–Y alloyAlloy . The initial APT analysis on the aged samples indicated that Ca segregated with Nd and Y in the precipitates in Mg–RE alloys.

Qianying Shi, Bruce Williams, John Allison

A Die-Cast Magnesium Alloy for Applications at Elevated Temperatures

The application of magnesium alloysMagnesium alloy (Mg alloy) in internal combustion engines has advantages of lightweight, better damping and noise reduction and less vibration during operation. However, the applications of magnesiumMagnesium pistons in internal combustion engines are still difficult due to the demanding work environment and the rigorous requirements of the increased mechanical performance, thermal conductivityThermal conductivity, and corrosion resistanceCorrosion resistance at elevated temperatures. The development of high temperature die-cast magnesium alloysMagnesium alloy (Mg alloy) for piston applications is therefore challenging, as the high temperature mechanical performance, the die casting capability, and the thermal conductivityThermal conductivity usually conflict with each other. Here we report a die-cast magnesium alloyMagnesium alloy (Mg alloy) for the piston applications at elevated temperatures, and the alloyAlloy development and the piston manufacturing process are introduced.

Xixi Dong, Eric A. Nyberg, Shouxun Ji

Effect of Gd and Nd Additions on the Thermo-Mechanical Response of a MgMn Alloy

AlloyingAlloy Mg with Mn improves the strength and corrosion resistanceCorrosion resistance. The addition of rare-earthRare earth elements weakens the textureTexture and improves the age hardeningAge hardening response. Nd and Gd are ideal elements to investigate the effect of low and high solid soluble rare-earthRare earth elements in Mg on the thermo-mechanical behaviorMechanical behavior of MgMn alloy. For this purpose, a Mg alloyMagnesium alloy (Mg alloy) with 1 wt% Mn and 1 wt% Nd was produced and then modified with the addition of 1 wt% Gd. In situ high-energy synchrotron X-ray diffractionDiffraction was performed during compression to analyse the deformation behaviorDeformation behavior of the material. The compression experiments have been performed at room temperature and 350 °C up to a deformationDeformation of 0.3 with a deformationDeformation rate of 10−3 s−1. The compressed samples were subsequently subjected to electron-backscattered diffractionDiffraction to investigate the post-mortem microstructureMicrostructure.

D. Tolnai, S. Gavras, P. Barriobero-Vila, A. Stark, N. Schell

Development of Ultra Lightweight, Corrosion Resistant Mg Alloys

The corrosionCorrosion behavior of BCC Mg–11Li–xGe (x = 0, 0.3, 0.5 wt%) alloys was evaluated in quiescent 3.5 wt% NaCl(aq) via potentiodynamic polarization, in situ optical imaging, and hydrogen volume capture in comparison with commercial Mg alloyMagnesium alloy (Mg alloy) AZ31B-H24. It is shown that Mg–11Li and Mg–11Li–0.3 Ge alloys possessed a lower corrosionCorrosion rate after 24 h immersion at open circuit potentialOpen circuit potential with respect to AZ31B-H24. Mg–11Li–0.3Ge alloyAlloy possessed the lowest corrosionCorrosion rate due to simultaneous reduction of cathodic kinetics and an improved pseudo passive film. Increasing the Ge concentration to 0.5 wt% was found to be detrimental to cathodic kinetics and passive film stability due to micro-galvanic coupling.

T. W. Cain, J. P. Labukas

Alloy Design and Solidification

Frontmatter

Insights on Solidification of Mg and Mg–Al Alloys by Large Scale Atomistic Simulations

We investigate the evolution of solid-liquid interfaces in Mg and Mg–9 at % Al during directional solidification by molecular dynamics (MD) simulations. At the initial stages of solidification, several solidification defects such as twins, stacking faults, and grain boundaries form, and at the final stages of solidification no new defects or grain boundaries form. The directional solidification in Mg–Al contains a considerable amount of heterogeneity due to formation of several Mg17Al12 precipitates.

Avik Mahata, Mohsen Asle Zaeem

Two-Stage Settling Approach to Purify Mg Alloy

Poor corrosion resistanceCorrosion resistance, especially galvanic corrosionCorrosion related to impurities, greatly limits the application of magnesium alloysMagnesium alloy (Mg alloy). In the current work, ironIron content distribution in Mg melts and solidified alloys, as well as settling velocity of Fe-containing particles during settling process, was calculated. Based on the calculation, a new purificationPurification process, two-stage settling method, was designed to purify the Mg alloyMagnesium alloy (Mg alloy) by reducing content of Fe impurities. The two-stage settling method was carried out using AZ91AZ91 alloyAlloy as the sample material.

Jiawei Liu, Tao Chen, Yuan Yuan, Jiajia Wu, Li Yang, Aitao Tang, Dajian Li, Fusheng Pan

CALPHAD Modeling and Microstructure Investigation of Mg–Gd–Y–Zn Alloys

In this study, CALculation of PHAse Diagrams (CALPHAD) CALPHAD (CALculation of PHAse DiagramsCALculation of PHAse Diagrams (CALPHAD)) modeling was used to design and optimize Mg–Gd–Y–Zn alloys containing long period stacking order (LPSO)Long Period Stacking Order (LPSO) phases. The selected compositions were evaluated using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffractionDiffraction to identify major phases and determine their area fractions. It was seen in as-cast samples that a blocky LPSOLong Period Stacking Order (LPSO) 14H phase formed at the grain boundaries while a filament-type LPSOLong Period Stacking Order (LPSO) 14H formed in the Mg grains. As the rare earthRare earth (RE) and Zn concentrations increased, eutectic Zn-rich intermetallics and more of the RE-rich blocky LPSOLong Period Stacking Order (LPSO) formed along grain boundaries. After annealing, an increase in the Zn-rich intermetallic area fraction, decrease in bulky LPSOLong Period Stacking Order (LPSO) area fraction, and increase in filament-type LPSOLong Period Stacking Order (LPSO) were observed. In higher alloyed samples, a Zn- and Y-rich phase was observed that was not consistent with the predicted or reported phase. These results indicate the present CALPHADCALculation of PHAse Diagrams (CALPHAD) databases well represent the LPSOLong Period Stacking Order (LPSO) 14H formation in the Mg–Gd–Y–Zn system studied and can be used to tailor the microstructureMicrostructure to potentially improve the strength and ductility in these alloys. Further investigation is needed to determine if the existing reliably databases modelModel the other secondary phasesSecondary phases.

Janet Meier, Josh Caris, Alan A. Luo

Intermetallic Phase Formation in Mg–Ag–Nd (QE) and Mg–Ag–Nd–Zn (QEZ) Alloys

The intermetallic phase (designated δ phase) in the solution-treated microstructureMicrostructure of commercial magnesium alloyMagnesium alloy (Mg alloy) QE22 (Mg–2.5Ag–2.0Nd–0.7Zr, wt%) has been investigated using scanning electron microscopy, electron diffractionDiffraction, atomic-resolution scanning transmission electron microscopy (STEM), and thermodynamic modelingThermodynamic modeling. In contrast to the previous reports, an orthorhombic structure (space group Cmcm) and a composition of NdAgMg11 are determined. The present experimental data are used to construct a thermodynamic description of the Mg–Ag–Nd system which is embedded in a multicomponent Mg alloyMagnesium alloy (Mg alloy) database. Implications on the formation of temperature range and thermal stability of this phase and alloyAlloy solidification are discussed based on the calculated Mg–Nd–Ag phase diagram and Scheil solidification paths of alloys. The impact of Ag-replacement in such QE alloys by Zn-addition in the Mg–Ag–Nd–Zn (QEZ) alloyAlloy system is elaborated using appropriate thermodynamic simulations to reveal the competition with other intermetallics. These data are suggested to contribute to ICMEICME of magnesium alloysMagnesium alloy (Mg alloy).

Rainer Schmid-Fetzer, Jian-Feng Nie, Xiaojun Zhao, Houwen Chen

Investigation on the Microstructure and Mechanical Properties of Mg–Gd–Nd Ternary Alloys

The present work deals with microstructureMicrostructure and mechanical propertiesMechanical properties of Mg–xGd–yNd (x = 10, 15; y = 2, 5) ternary alloys. Hardness, tensile, and compressive properties are measured on the as-cast alloys and the alloys after solid solution treatment (T4 state). The hardness, tensile yield stress (TYS), and ultimate tensile stress (UTS) are increased with increasing amount of alloying elements for both as-cast and T4 state. The elongation (El) of alloys is lower with higher Nd content. The compressive properties of all studied alloys are increased by T4 treatment. With increasing of alloyAlloy concentration, both compressive yield stress (CYS) and ultimate compressive stress (UCS) of alloys are enhanced, but the compressibility is decreased. Intermetallic compounds which appear along the grain boundary are reduced after T4 treatment for alloys with 2% Nd. However, large amount of intermetallic compounds with high Nd concentrations remains on the grain boundary of Mg–xGd–5Nd alloys.

Yuling Xu, Lixiang Yang, Weili Liu, Jingli Sun, Lu Xiao, Xianquan Jiang, Norbert Hort

Recrystallization Effects on the Forming Behaviour of Magnesium Alloy Sheets with Varied Calcium Concentration

The formation of strong textures with a preferential alignment of the basal planes in the sheet plane was an important disadvantage for the formabilityFormability of magnesium alloyMagnesium alloy (Mg alloy) sheets. Rare earthRare-earth or calciumCalcium-alloying concepts allow significant textureTexture changes during rollingRolling, resulting in weaker textures, and thus improved the formabilityFormability. Such a textureTexture development has also been associated with retarded recrystallizationRecrystallization. However, this retardation affects the formabilityFormability during sheet forming operations at elevated temperature. The wrought alloyAlloy AZ31 and its Ca-modified counterpart AZX310 are used for Nakajima forming tests at different temperatures. The influence of recrystallizationRecrystallization on the sheet formabilityFormability is demonstrated along different strain paths including local microstructureMicrostructure analysis. The weaker textureTexture due to the addition of Ca allows maintaining the improved formabilityFormability, which is counteracted by retarded recrystallizationRecrystallization.

Jan Bohlen, Huu Chanh Trinh, Klaus Rätzke, Sangbong Yi, Dietmar Letzig

Towards the Development of High Ductility Mg–Al Based Alloys Through Second-Phase Refinement with Trace Yttrium Additions

Magnesium alloysMagnesium alloy (Mg alloy) are attractive lightweight materialsMaterials for transportation industry as they offer a viable approach for reduced CO2 emissions and fuel economy. The most widely used alloys for automotive applications are based on the Mg–AlMg–Al system where the principal second-phase β-Mg17Al12 provides strengthening but reduces ductility. A key factor in widening the use of magnesiumMagnesium in crashworthy components such as vehicle body applications is the availability of cost-effective Mg casting alloys with improved ductility. Modification of the Mg17Al12 in Mg–AlMg–Al alloys via trace additions is a promising approach to enhance the ductility while maintaining the strength. Our research has found that only trace levels of yttrium (Y) can modify the Mg17Al12 and improve the ductility of Mg–6Al alloyAlloy by 63%. To elucidate the mechanism of this refinement, different methodsMethods are used including thermodynamic calculationsThermodynamic calculations, image analysis, scanning and transmission electron microscopy.

Konstantinos Korgiopoulos, Mihriban Pekguleryuz

Design of Heat-Dissipating Mg–La–Zn Alloys Based on Thermodynamic Calculations

HowThermodynamic calculations to design alloys with good heat-dissipating capacity and predict the thermal conductivities of Mg–La–Zn alloysMg–La–Zn alloys is an interesting and important topic. In this study, nine alloys were designed by thermodynamic phase diagram calculations in Mg–La–Zn system. Their compositions were determined by controlling phase components and the solid solubility of Zn in α-Mg. The temperature dependence of thermal conductivities of as-cast Mg–xLa–yZn (x = 0.18–0.37 at.%, y = 0–2.55 at.%) alloys were investigated using flash method. Phase compositions and microstructureMicrostructure of heat-dissipating Mg–La–Zn alloysMg–La–Zn alloys were also analyzed using X-ray diffractionDiffraction and scanning electron microscopy. Considering the thermal conductivityThermal conductivity of single-phase LaMg12 alloyAlloy measured in the present work, the thermal conductivities of Mg–La–Zn alloysMg–La–Zn alloys in the two-phase regions (α-Mg + LaMg12) were also evaluated using the CALPHADCALculation of PHAse Diagrams (CALPHAD) method. Results indicated that the Mg–La–Zn alloysMg–La–Zn alloys with secondary phase (LaMg12) exhibited higher thermal conductivityThermal conductivity than those with τ1, and the high solid solubility of Zn in α-Mg was detrimental to the heat dissipation of Mg alloysMagnesium alloy (Mg alloy). Meanwhile, the calculated thermal conductivities show good agreements with the corresponding experimental values.

Hui Shi, Qun Luo, Qian Li, Jieyu Zhang, Kuo-Chih Chou

Effects of Zn Additions on the Room Temperature Formability and Strength in Mg–1.2Al–0.5Ca–0.4Mn Alloy Sheets

We investigated the effects of Zn additions on the mechanical propertiesMechanical properties and microstructureMicrostructure of Mg–1.2Al–0.5Ca–0.4Mn and Mg–1.2Al–0.5Ca–0.4Mn–1.6Zn (wt%) alloyAlloy sheets fabricated by twin-roll castingTwin-roll casting and conventional hot rollingRolling . The room temperature stretch formabilityFormability of the solution-treated alloyAlloy sheet is improved by the addition of Zn. The Mg–1.2Al–0.5Ca–0.4Mn–1.6Zn alloyAlloy shows an excellent stretch formabilityFormability with the larger Index Erichsen valueErichsen value of 8.2 mm due to a weak transverse direction split textureTexture . The development of the weak textureTexture is attributed to the uniform grain growth by the solute segregation to the recrystallizationRecrystallization grain boundaries. Subsequent bake-hardeningBake-hardening treatment, 2% pre-strain at 170 °C for 20 min leads to substantial increase in strength without the loss of ductility. The bake-hardened Mg–1.2Al–0.5Ca–0.4Mn–1.6Zn alloyAlloy exhibits a high tensile yield strength of 235 MPa with an elongation to failure of 27.1%.

Z. H. Li, T. T. Sasaki, M. Z. Bian, T. Nakata, Y. Yoshida, N. Kawabe, S. Kamado, K. Hono

Fundamentals, Mechanical Behavior, Twinning, Plasticity, and Texture I

Frontmatter

An Investigation into the Role of Dislocation Climb During Intermediate Temperature Flow of Mg Alloys

Textured Mg alloyMagnesium alloy (Mg alloy) sheetDislocation samplesMagnesium alloy (Mg alloy) were tensile tested parallel to the transverse direction, at Zener–Hollomon parameter values ranging from Z ~ 50 at room temperature and 10−3 s−1 down to Z ~ 18 at 350 °C and 10−5 s−1. At high Z, the samples exhibit strong texture evolutionTexture evolution indicative of significant prismatic slip of dislocations with <a> Burgers vectors. Correspondingly, the plastic anisotropyPlastic anisotropy is high, r ~ 4. At low Z, the texture evolutionTexture evolution is minimal and the response is nearly isotropic, r ~ 1. Previously, it has been asserted that the high ductility and low plastic anisotropyPlastic anisotropy observed at low Z conditions is due to enhanced activity of non-basal slip modes, including prismatic slip of <a> dislocations and pyramidal slip of <a> and <c+a> dislocations. The present results call this understanding into question and suggest that the enhanced ductility is more closely associated with the climbClimb of <a> dislocations.

Michael A. Ritzo, Jishnu J. Bhattacharyya, Ricardo A. Lebensohn, Sean R. Agnew

Deviations from Theoretical Orientation Relationship Along Tensile Twin Boundaries in Magnesium

DeformationDeformation twinningTwinning is a prevalent mode of plastic deformationDeformation in hexagonal close packed (HCP) magnesiumMagnesium. Twin domains are associated with significant lattice reorientation and localized shear. The theoretical misorientationMisorientation angle for the most common $$ \left\{ {10\overline{1} 2} \right\}$$ tensile twin in magnesiumMagnesium is 86.3°. Through electron backscatter diffractionDiffraction characterization of twinningTwinning microstructureMicrostructure, we show that the twin boundary misorientationMisorientation at the twin tips is approximately 85°, and it is close to the theoretical value only along the central part of the twin. The variations in twin/matrix misorientationMisorientation along the twin boundary control the twin thickening process by affecting the nucleation, glide of twinningTwinning partials, and migration of twinningTwinning facets. To understand this observation, we employ a 3D crystal plasticityCrystal plasticity modelModel with explicit twinningTwinning. The modelModel successfully captures the experimentally observed misorientationMisorientation variation, and it reveals that the twin boundary misorientationMisorientation variations are governed by the local plasticityPlasticity that accommodates the characteristic twin shear.

B. Leu, M. Arul Kumar, Y. Liu, I. J. Beyerlein

The Role of Faceting in Twin Nucleation

{1012} twinningTwinning is the most profuse twin mode in Mg and plays a major role in its plasticityPlasticity and deformationDeformation . Identification of the mechanisms and locations of twinning nucleation is crucial to characterize the ensuing microstructural evolutionMicrostructural evolution and failure. Herein, we provide a new theory of hexagonal close-packed twin nucleation. In essence, the theory is that twins need a pre-existing interface upon which to grow. In the earliest stages of nucleation, this requirement implies that the twin must be able to facet onto the same plane as the local interface, whether it be a free surface, stacking fault, or grain boundary, and that the action of twinningTwinning must reduce the defectDefects energy of the pre-existing structure in order to remain stable until it can grow large enough to emit disconnections. The theory is demonstrated on {1012} twin nucleation at grain boundaries and stacking faults in Mg via molecular dynamics.

Christopher D. Barrett

In Situ TEM Investigation of Dislocations in Magnesium

The ductility of magnesiumMagnesium is intimately related to $$ \left\langle {c + a} \right\rangle $$ dislocationDislocation. Understanding the behavior of $$ \left\langle {c + a} \right\rangle $$ dislocations is of critical importance for resolving the mechanical propertiesMechanical properties and for alloyAlloy design. By using in situ TEMIn situ TEM mechanical testing of pillars of pure Mg single crystal, we found that $$ \left\langle {c + a} \right\rangle $$ dislocationDislocation can accommodate considerable plasticityPlasticity. Our findings provide information on the mobility of $$ \left\langle {c + a} \right\rangle $$ dislocationDislocation and its relationship with plasticityPlasticity of submicron-sized pure Mg. The experimental strategy can be extended to understanding the dislocationDislocation behaviors in other hexagonal metals.

Bo-Yu Liu, Fei Liu, Bin Li, Jian-Feng Nie, Zhi-Wei Shan

Full-Field Crystal Plasticity Modeling of Twin Nucleation

Historically, the ability of crystal plasticityCrystal plasticity to incorporate the Schmid’s law at each integration point has been a powerful tool to simulate and predict slip-induced localization at the single and polycrystal levels. Unfortunately, this remarkable capability has not been replicated for materialsMaterials where twinningTwinning becomes a noticeable deformationDeformation mechanismDeformation mechanism. The challenge resides mainly in the biased regional lattice transformation associated with twin formation in defiance of its obedience to threshold stress. Inspired by results from micromechanicsMicromechanics, digital image correlation, and molecular dynamics, we developed an explicit twinning nucleation criterion based on hydrostatic stress gradient and volume fraction of twin inside a grain. Characteristic twin spacing parameter is used as a function of twin height to determine site-specific nucleation points in the case of multiple twins. This approach offered a good reproduction of the microstructureMicrostructure evolution and autocatalysis phenomenon as affected by twinningTwinning in a tricrystal system.

YubRaj Paudel, Christopher D. Barrett, Haitham El Kadiri

The Incorporation of Discrete Deformation Twins in a Crystal Plasticity Finite Element Framework

The most prevalent twinning models homogenize the local deformation response by considering twins as “pseudoslip” systems, obscuring the physical differences between slip and twinning—namely the discrete nature of twinning. Presented is a computational approach designed to consider discrete deformation twinning in a crystal plasticity finite element framework. A polycrystalline domain is pre-discretized at the sub-grain scale into lamellar regions dependent on the geometry of the twin systems, which facilitates a finite element mesh that is attendant to this geometry. A twin is activated in a lamellar region by applying essential velocities to its nodes and rapidly mapping their locations to their expected twinned positions. The rest of the body deforms by crystallographic slip to enforce mechanical equilibrium. Results indicate stress relaxation in the parent grain and regions of large stress concentrations in neighboring grains. These trends are discussed in light of global and local energetic observations.

Matthew Kasemer, Paul Dawson

On the Load Multiaxiality Effect on the Cyclic Behaviour of Magnesium Alloys

While most fatigue-related studies on wrought magnesium alloysMagnesium alloy (Mg alloy) are under uniaxial push–pull loading condition, structural members are mostly under multiaxial stresses in real-life applications. This study addresses the effect of load multiaxiality on the cyclic behaviour of several wrought magnesium alloysMagnesium alloy (Mg alloy): AZ31B, AM30, AZ80, and ZK60 under multiaxial tension/compression–torsion loading. In particular, the influence of the presence of shear on normal stress response and vice versa is studied. In addition, phase angle effects on the stress–strain response and fatigue life are discussed. Strain energy density (SED) is introduced as a suitable fatigue damage parameter to connect and compare uniaxial and multiaxial cases. It is shown that irrespective of loading direction and/or phase angle, SED closely correlates experimental results. Beyond strain of ~0.4–0.5%, the strain-controlled cyclic behaviour in uniaxial push–pull is dominated by twining/de-twinningTwinning, while in pure shear deformationDeformation is dominated by basal slip. The effect of each of these load directions on the other in a multiaxial loading is considered in two cases: at low axial strain amplitudes the interaction is mutual, and at high axial strain amplitudes axial strain dominates. It is believed that the re-orientation of basal planes due to twinningTwinning/de-twinningTwinning caused by axial strain favours basal slip in twinned grains resulting in better accommodation of shear strain. Further, three load phase angles of 0, 45, and 90 were considered. It is observed that the phase angle has minimal effect on life at low axial strain values; however, at higher axial strain amplitudes out-of-phase angle causes more damage. The re-orientation of matrix due to twinningTwinning and rotation of the principal axis due to phase angle shift increase the chance of different slip/twin systems to be activated resulting in lower lives.

A. Gryguć, S. M. H. Karparvarfard, A. Roostaei, D. Toscano, S. Shaha, B. Behravesh, H. Jahed

Thermomechanical Processing

Frontmatter

Deformation Driven Precipitation in Binary Magnesium Alloys

Unlike Aluminum (Al) alloys, precipitation strengthening of Magnesium (Mg) alloys has proven challenging. Precipitate density is typically too low, and precipitate size is often too large and elongated to enhance the resistance to plastic deformation significantly. Mimicking recent work in Al alloys, we are exploring how low-temperature plastic deformation can enhance the density, size, and morphology of common intermetallic particles and thereby lead to significant hardening in Mg alloys. The low temperatures tend to favor nucleation overgrowth, while the deformation provides vacancies and dislocations that can assist nucleation. Using equal channel angular extrusion, and moderate temperatures, we explore the processing and thermodynamic factors controlling nucleation and growth of precipitates in Mg–Al and Mg–Zn binary alloys.

Suhas Eswarappa Prameela, Timothy P. Weihs

Effect of Second Phase Particle Size on the Recrystallized Microstructure of Mg–Al Alloys Following ECAE Processing

Magnesium (Mg) alloysMagnesium alloy (Mg alloy) areEffect of second phase particle size excellentMicrostructure candidates for structural applications, given their high strength to weight ratios. Grain boundaries and precipitates can both contribute to strengthening in Mg alloysMagnesium alloy (Mg alloy) , but the design of high strength Mg alloysMagnesium alloy (Mg alloy) is challenging due to Mg’s anisotropic crystal lattice and yield asymmetry. Herein, we focus on thermomechanical processing that involves grain refinementGrain refinement in the presence of precipitates. We seek an understanding of how small and large Mg17Al12 intermetallic particles impact recrystallizationRecrystallization and discontinuous precipitationPrecipitation in Mg–AlMg–Al alloys. We do so by processing solution treated and peak aged Mg–9Al (wt%) alloys using equal channel angular extrusionExtrusion (ECAE) along the Bc route at 150 °C. We find that the fine nanoprecipitates that nucleate within the solutionized grain interiors during ECAE processing lead to finer Mg grains in the recrystallized regions compared to those in the presence of the long lathlike precipitates produced during peak aging prior to ECAE processing.

Suhas Eswarappa Prameela, Peng Yi, Vance Liu, Beatriz Medeiros, Laszlo J. Kecskes, Michael L. Falk, Timothy P. Weihs

Relating Texture and Thermomechanical Processing Variables in Mg–Zn–Ca Alloys

ItMg-Zn is well known that the strong basal textureTexture commonly produced in magnesium alloyMagnesium alloy (Mg alloy) sheets leads to poor formabilityFormability at room temperature. A sizable body of work has explored how changing the alloyAlloy composition and rollingRolling conditions can yield more desirable textures; however, important thermomechanical variables, such as the feed rate during rollingRolling , are often not included in the literature, making it difficult to correlate how changes in processing affect the final crystallographic textureCrystallographic texture . This work explores the texture evolutionTexture evolution and grain refinementGrain refinement in Mg–ZnMg-Zn –Ca alloys during plane strain compression (PSC) using a GleebleGleeble thermomechanical simulator. This instrument allows for precise control and capture of the thermomechanical history of the sample. The textureTexture and grain morphology of the compressed samples were characterized using electron backscatter diffractionDiffraction (EBSD). The textureTexture results will be used to identify which alloys and processing conditions should be scaled up for future rollingRolling studies.

Tracy D. Berman, John E. Allison

Variation of Extrusion Process Parameter for the Magnesium Alloy ME21

ExtrusionExtrusion is an economic production process for the generation of semi-finished magnesiumMagnesium products that can be used for biomedical and automotive applications. This paper reports on the variation of process parameters (temperature and extrusionExtrusion speed) in the aluminum-free magnesium alloyMagnesium alloy (Mg alloy) ME21 (Mg–2Mn–0, 6Ce–0,3) during extrusionExtrusion in order to investigate their influence on strength and ductility of the produced profiles. The influence of the varied process parameters on the microstructureMicrostructure before and after heat treatmentHeat treatment is shown. Furthermore, the mechanical propertiesMechanical properties of the extruded profiles are presented and discussed with respect to arising textures. The results of this work are used to discuss how to tailor the mechanical propertiesMechanical properties of the magnesium alloyMagnesium alloy (Mg alloy) ME21 during the extrusionExtrusion process.

G. Kurz, M. Nienaber, J. Bohlen, D. Letzig, K. U. Kainer

Asymmetric Rolling of TZ73 Magnesium Alloy to Improve Its Ductility

Asymmetric rollingAsymmetric rolling , i.e., upper and lower rolls having different circumferential speeds, is a novel technique to improve the ductility of Mg alloysMagnesium alloy (Mg alloy) . A newly developed TZ73 Mg alloyMagnesium alloy (Mg alloy) was squeeze cast, homogenized at 300 °C for 24 h, rolled at 350 °C by symmetric and asymmetric rollingAsymmetric rolling , and annealed at 215 °C for 30 min. The microstructureMicrostructure was characterized by X-ray diffractionDiffraction , scanning electron microscope equipped with energy-dispersive X-ray spectroscopy and electron backscattered diffractionDiffraction . A weakening of basal textureTexture with a concomitant increase in ductility was observed for asymmetrically rolled sheet while retaining the same strength as in symmetrically rolled sheet. Thus, tensile propertiesTensile properties of 0.2% PS = 290 MPa, UTS = 332 MPa and El = 13% in hot rolled, and 0.2% PS = 182 MPa, UTS = 282 MPa and El = 21% in annealed condition were obtained for asymmetrically rolled sheet, which are extremely good for a rolled Mg alloyMagnesium alloy (Mg alloy) sheet.

Krishna Kamlesh Verma, Satyam Suwas, Subodh Kumar

Friction Stir Processing of Magnesium Alloy with Spiral Tool Path Strategy

Friction stir processingFriction stir processing is a relatively new technique for microstructural modification to improve the mechanical propertiesMechanical properties of materialsMaterials . Previous works have been primarily focused on the processing of the small regions. The objective of this work is to study the effect of tool designTool design , tool rotation direction and tool overlap between passes on the processed region. A spiral tool path strategyTool path strategy is employed to process the complete blanks of a magnesium alloyMagnesium alloy (Mg alloy) . Three tool designs: tool with hexagonal, tapered and threaded pin, are used. Further, tool rotation direction and tool overlap between passes are varied across the experiments. The material flow and defectsDefects formed in the processed region are characterized. Preliminary results show that tool rotation direction and tool overlap significantly affect the defectsDefects formed in the processed region. The present work identifies the processing condition for defect-free processed region and refined microstructureMicrostructure of the MagnesiumMagnesium blank.

Abhishek Kumar, Aarush Sood, Nikhil Gotawala, Sushil Mishra, Amber Shrivastava

Joining Dissimilar Materials via Rotational Hammer Riveting Technique

AMaterials robustRiveting, economically viable joining method for Mg/Al and Mg/CFRPCarbon Fiber Reinforced Polymer (CFRP) could enable multi-material assemblies that decrease vehicle weight while offering more flexibility for designers. However, certain challenges exist for joining Mg/Al and Mg/CFRPCarbon Fiber Reinforced Polymer (CFRP). Mechanical joining, such as conventional rivetingRiveting, clinching and bolting do not form a metallurgical bond between the fastener and metal sheet being fastened. Large differences in physical and mechanical propertiesMechanical properties of metals and polymers make joining Al or Mg to CFRPCarbon Fiber Reinforced Polymer (CFRP) challenging via various welding techniques. For Mg/Al pair, solid-phase and fusion-based welding results in rapid formation of brittle intermetallic compounds at the interface leading to premature interfacial fracture under mechanical loading. In this study, a Rotational Hammer Rivet (RHR) technique was developed to fabricate Mg/CFRPCarbon Fiber Reinforced Polymer (CFRP) and Mg/Al joints. With RHR technique, direct joining between Mg/Al and Mg/CFRPCarbon Fiber Reinforced Polymer (CFRP) were replaced by joining Mg rivet head and top Mg sheet. Through heat generated by plastic deformationDeformation of an Mg rivet, RHR creates a metallurgical bond between rivet head and Mg sheet which seals corrosive electrolyte from penetrating around the rivet head.

Tianhao Wang, Scott Whalen, Piyush Upadhyay, Keerti Kappagantula

Corrosion

Frontmatter

Anomalous Hydrogen Evolution on Magnesium

When Mg undergoes anodic polarization in a corrosive environment, the rate of hydrogen evolution (HE) increases with increasing applied anodic potential or current, which is opposite of the expected behavior based on standard electrochemical kinetics. This anomalous HE has been the recent focus of researchers worldwide. In this work, the behavior of sputtered Mg thin films and scratched Mg electrodes is presented. HE vanished when the potential of a pit in Mg thin films was increased into the region where a salt film formed. The peak anodic current on scratched samples was not anomalous, as it decreased slightly with increased potential. These observations indicate that the HE rate on Mg depends on the nature of the surface and that anomalous HE results from the surface being more catalytic to the HE reaction with increasing dissolution rate.

Aline D. Gabbardo, G. S. Frankel

Numerical Investigation of Micro-Galvanic Corrosion in Mg Alloys: Role of the Cathodic Intermetallic Phase Size and Spatial Distributions

Magnesium alloysMagnesium alloy (Mg alloy) areMicro-galvanic corrosion ofMagnesium alloy (Mg alloy) increasing interest in structural applications due to their low-density, moderate specific strength and stiffness, recyclability, and high damping among other properties. However, the wide-scale applicability of magnesium alloysMagnesium alloy (Mg alloy) in structural applications has been limited due to many factors including its poor corrosion resistanceCorrosion resistance . In this work, a numerical investigation to simulate the micro-galvanic corrosionMicro-galvanic corrosion behavior was performed to examine the influence of the size and distribution of cathodic intermetallic phase (β–Mg17Al12) in a Mg matrix. The ratio of cathodic to anodic surface area was kept constant in each simulation condition to understand the effect of size and spacing distributions. In general, fragmentationFragmentation of a larger intermetallic particle into smaller ones was determined to enhance the localized current density. However, the uniform distribution rather than clustered or non-uniform distribution of this small intermetallic phase throughout the matrix was found to reduce the overall dissolution current density and hence, pitting corrosionCorrosion severity.

V. K. Beura, P. Garg, V. V. Joshi, K. N. Solanki

The Corrosion Behavior of High Purity Mg According to Process History

This study paid attention to the big difference between the corrosionCorrosion rates of permanent mold cast and hot-extruded pure Mg. Fe existed as different state according to process history, which affected the corrosionCorrosion behavior of pure Mg largely. The corrosionCorrosion rate of high purityHigh purity Mg was measured extremely low when Fe was dissolved into the matrix as a solid solution while it increased dramatically when Fe was precipitated as a second phase. The precipitationPrecipitation behavior of the second phase containing Fe was affected by other impurities as much as thermal history, which affected the corrosionCorrosion behavior of high purityHigh purity Mg. It is suggested from this study that the tolerance limit of Fe is strongly dependent on the content of Fe, the sort and content of other impurities and process history, which should be considered to design the composition and processing route of high corrosionCorrosion -resistant Mg alloyMagnesium alloy (Mg alloy) .

Sang Kyu Woo, Byeong-Chan Suh, Nam Ryong Kim, Ha Sik Kim, Chang Dong Yim

Design of the Magnesium Composite with High Corrosion Resistance and High Deformability

MagnesiumMagnesium is one of the most promising lightweight materialsMaterials. However, its competitiveness has been severely reduced by the poor corrosion resistanceCorrosion resistance, low strength, poor deformability, and formabilityFormability. Here, we propose to design a novel magnesiumMagnesium-based composite prepared by the powder metallurgyPowder metallurgy using the magnesiumMagnesium nanoparticles with a MgCO3 protective layer, which can be obtained via the transformation from the native or corroded surface at room temperature and may effectively improve the anti-corrosionAnti-corrosion as well as deformability of submicron-scale magnesiumMagnesium.

Yue-Cun Wang, Bo-Yu Liu, Zhi-Wei Shan

Advanced Immersion Testing of Model Mg-Alloys for Biomedical Applications

The acceleration of developing magnesium alloysMagnesium alloy (Mg alloy) forModel biomedicine requires the advancement of experimental methodsMethods evaluating their performance. We have been developing an advanced immersion testingImmersion testing method for the assessment of biomedical Mg alloyMagnesium alloy (Mg alloy) degradationDegradation in aqueous environments. It is based on the combination of isothermal calorimetryIsothermal calorimetry with pressure measurement in the reaction cell. Such a combination allows in situ quantitative analysis of chemical reactions based on both the enthalpy (heat) of the process itself and hydrogen gas generated as one of the reaction products. Here, we analyze the evolution of the degradationDegradation rate of a ternary Mg–5.0Zn–0.3Ca intended for biomedical applications and two modelModel binary Mg–5.0Zn and Mg–0.3Ca alloys (in as-cast and solutionized states) in 0.9% NaCl water solution and a simulated body fluid (SBF)Simulated Body Fluid (SBF) . The results obtained using the novel method are critically compared to more traditional immersion testingImmersion testing with hydrogen collection.

Dmytro Orlov, Bastien Reinwalt, Ilyes Tayeb-Bey, Lars Wadsö, Jelena Horky, Andrea Ojdanic, Erhard Schafler, Michael Zehetbauer

Effect of 2 wt% Ag Addition on Corrosion Properties of ZK40 for Biodegradable Applications

The antibacterial effects of silverSilver make it an attractive alloying element for biodegradable Mg alloysMagnesium alloy (Mg alloy) to treat possible inflammation and infections caused by the degrading orthopedic implants. In this study, as-extruded Mg–4%Zn–0.5%Zr (ZK40) alloyAlloy was alloyed with Ag, specifically 2 wt%, and subjected to a heat treatmentHeat treatment at 350 ℃ for 7 days. The mechanical and corrosionCorrosion responses were studied in two orthogonal planes (transverse and extrusionExtrusion) before and after silverSilver addition to explore its potential for biodegradable orthopedic applications. CorrosionCorrosion characteristics were assessed at 37 ℃ in Hank’s solution for 24 h via electrochemical impedance spectroscopy (EIS)Electrochemical Impedance Spectroscopy (EIS), potentiodynamic polarization (PD) and open circuit potentialOpen circuit potential (OCP). As-extruded and heat-treated ZK40 alloyAlloy displayed an inhomogeneous microstructureMicrostructure containing large, coarse grains, Zn–Zr rich secondary phase and some fine grain regions. While in ZK40–Ag, both planes showed a relatively more homogenous microstructureMicrostructure but with some agglomeration of Zn–Ag rich secondary phasesSecondary phases. Here, we present our initial results on the different corrosionCorrosion behaviors observed in the two materialsMaterials.

M. AbdelGawad, B. Mansoor, M. W. Vaughan, I. Karaman

Study of In Vitro Biodegradation Behavior of Mg–2.5Zn–xES Composite

In this study, zinc (Zn) and eggshell (ES) reinforced biodegradable magnesium alloyMagnesium alloy (Mg alloy) (Mg–2.5Zn) and environment concise (eco) composite (Mg–2.5Zn–xES) was fabricated using disintegrated melt deposition (DMD)Disintegrated Melt Deposition (DMD) technique. In vitro experiments were conducted to study the biodegradationBiodegradation behavior of Mg–2.5Zn and Mg–2.5Zn–xES (x = 3 and 7 wt%) using simulated body fluid (SBF)Simulated Body Fluid (SBF) under standard human body temperature of 37 ℃. Using electrochemical Impedance Spectroscopy (EIS)Electrochemical Impedance Spectroscopy (EIS), electrochemical analysis was performed to study in vitro degradationDegradation behavior of alloyAlloy and composite. EISElectrochemical Impedance Spectroscopy (EIS) revealed increased in vitro degradationDegradation of the biodegradable magnesium alloyMagnesium alloy (Mg alloy) and ecofriendly composite as percentage of ES reinforcement was increased. X-ray diffractionDiffraction (XRD) was performed to observe the chemical composition of elements and reaction products present in the degraded samples after corrosionCorrosion process. Scanning electron microscopy (SEM) analysis showed variations in surface morphology of the alloyAlloy and composite before and after degradationDegradation. SEM result revealed presence of defectsDefects in the tested samples after degradationDegradation process.

Srinivasan Murugan, Paul C. Okonkwo, Ahmed Bahgat, Gururaj Parande, Aboubakr M. Abdullah, Manoj Gupta

Corrosion Behavior of Squeeze Cast Mg Alloy AM60-Based Hybrid Nanocomposite

Micron-sized alumina (Al2O3) short fibreMicron-sized alumina (Al2O3) short fibre and/or nano-sized alumina (Al2O3) particlesNano-sized alumina (Al2O3) particles were squeezed cast into Mg AM60 alloyAlloy . Two types of 7 vol.% Fibre/AM60, and (7 vol. % Fibre + 3 vol.% nano-particle)/AM60 composites, as well as the unreinforced matrix alloyAlloy were prepared. The corrosionCorrosion behaviors of the composites as well as the unreinforced matrix alloyAlloy were investigated by using the potential dynamic polarization test. Compared with the matrix alloyAlloy , the introduction of micron-sized alumina fibres decreased the corrosion resistanceCorrosion resistance of Mg alloyMagnesium alloy (Mg alloy) AM60 considerably due to the presence of excessive interfaces between the fibre and matrix. The high density of grain boundaries and the absence of noble precipitates such as β-Mg17Al12 phases and Al–Mn intermetallics at the grain boundaries in the composites should be for the reduction in their corrosion resistanceCorrosion resistance . The addition of the nano-sized particles led to almost no further reduction in the corrosion resistanceCorrosion resistance of the composite.

Xinyu Geng, Luyang Ren, Zixi Sun, Henry Hu, Xueyuan Nie

Solidification and Production of Magnesium

Frontmatter

Thermodynamic Descriptions of the Quaternary Mg–Al–Zn–Sn System and Their Experimental Validation

A brief review on the thermodynamic descriptions of all the sub-binary and ternary systems in the Mg–Al–Zn–SnMg-Al-Zn-Sn system available in the literature was first performed, from which the most reliable ones were chosen. After that, thermodynamic description of the quaternary Mg–Al–Zn–SnMg-Al-Zn-Sn system was established via the direct extrapolation of the chosen thermodynamic descriptions of the sub-binary and ternary systems in the framework of CALculation of PHAse Diagrams (CALPHAD)CALculation of PHAse Diagrams (CALPHAD) approach. The reliability of the established thermodynamic database was finally validated through a comprehensive comparison of the modelModel -predicted solidified microstructureMicrostructure characteristics and phase fractions in different quaternary alloys with the experimental ones.

Ting Cheng, Lijun Zhang

Investigation and Modelling of the Influence of Cooling Rates on the Microstructure of AZ91 Alloys

An increasingly important tool in modern experimental investigations is the ability to accurately produce a digital modelModel or “digital twinDigital twin” of samples and their properties. This goes hand-in-hand with the primary tenant of Industry 4.0 which is to provide advanced manufacturing solutions through the use of cyber-physical systems. A comparison of various quenchingQuenching media, namely liquid nitrogen, water at 5 ℃, water at 20 ℃ and in the air on the microstructureMicrostructure of permanent mould cast AZ91AZ91 alloys was investigated. Particular emphasis was centred on the changes in microstructural features such as grain size and dendrite arm spacing. Phase-field method was used to produce a digital twinDigital twin and qualitative analysis of the investigated cooling rates on AZ91AZ91. The combination of practical microstructural investigations and the simulated microstructures will advance the knowledge of cooling rate influences on AZ91AZ91 and their ability to be accurately simulated to assist with property and microstructural predictions.

S. Gavras, M. U. Bilal, D. Tolnai, N. Hort

The Independent Effects of Cooling Rate and Na Addition on Hydrogen Storage Properties in Hypo-eutectic Mg Alloys

TheHydrogen storage properties additionMagnesium alloy (Mg alloy) of trace concentrations of elements such as Na and Sr along with rapid cooling is well-established methodMethods for modification of the faceted eutectic Si in Al–Si. There have been some efforts to extend this strategy to Mg-based alloys. For example, it has been reported that trace Na addition to Mg–Ni alloys can also refine the eutectic Mg2Ni phase and facilitate functional property improvements such as hydrogen absorption kineticsHydrogen absorption kinetics. In this work, we have extended this strategy to a variety of other Mg-based alloys such as Mg–Ni and Mg–La alloys through the addition of trace elements and use of different cooling rates. The modification of the eutectic morphology in these alloys is discussed with regard to the Jackson parameters which were calculated using data from Thermo-Calc. The relationship between eutectic modificationEutectic modification and hydrogen absorption kineticsHydrogen absorption kinetics in these alloys is investigated. The work has demonstrated, contrary to prior expectations, that microstructural refinement and hydrogen absorption kineticsHydrogen absorption kinetics are not necessarily correlated.

Manjin Kim, Yahia Ali, Stuart D. McDonald, Trevor B. Abbott, Kazuhiro Nogita

Producing High Purity Magnesium (99.99%) Directly by Pidgeon Process

Pure magnesiumMagnesium isHigh purity theMagnesium foundation of the entire magnesiumMagnesium industry. Over 90% of the pure magnesiumMagnesium on the market is produced in China using Pidgeon processPidgeon process . Even though the quality of pure magnesiumMagnesium has been improved significantly in the past decades, the majority of them is still suffering the following problems: The purity is only ~99.9%; there are still too many kinds of harmful impurityImpurity elements with their content fluctuating greatly in an uncontrollable manner. The impurities can be passed to magnesium alloysMagnesium alloy (Mg alloy) and degrade their properties significantly, especially their corrosion resistanceCorrosion resistance ability. This leaves people an impression that Pidgeon processPidgeon process cannot produce high purityHigh purity magnesiumMagnesium directly. As a consequence, it has long been accepted that producing high purityHigh purity magnesiumMagnesium requires additional processes, which is usually costly and time-consuming. After analyzing the impurities’ source of the Pidgeon processPidgeon process , we developed a new technique that can produce high purityHigh purity magnesiumMagnesium (99.99%) directly by Pidgeon processPidgeon process without significantly increasing the costs. The application of this new technique is expected to benefit the entire magnesiumMagnesium industry.

Bo Yang, Fei Liu, Bo-Yu Liu, Zhi-Min Chang, Lu-Yao Mao, Jiao Li, Zhi-Wei Shan

Research on Properties of Prefabricated Pellets of Silicothermic Process After Calcination in Flowing Argon Atmosphere

In the Pidgeon processPidgeon process, the separation of calcinationCalcination and reduction process leads to a long production cycle and high energy consumption. Based on the novel preparation method of pellets of silicothermic processSilicothermic process, the low-grade magnesite with abundant resources in Liaoning Province was used as raw material, calciumCalcium source, reducing agent, and fluorite were added to pelletizer directly and then calcined and reduced in flowing argonFlowing argon atmosphere. The properties and micromorphology of prefabricated pelletsPrefabricated pellets after calcinationCalcination were investigated in the work. The experimental results showed that the hydration activity and compressive strength of prefabricated pelletsPrefabricated pellets after calcinationCalcination reached 23.0% and 998 N, respectively. The recovery ratio of magnesiumMagnesium metal was more than 80% in the reduction process. The research on calcinationCalcination of prefabricated pelletsPrefabricated pellets in flowing gas provided a theoretical basis for continuous extraction of magnesiumMagnesium.

Junhua Guo, Ting’an Zhang, Daxue Fu, Jibiao Han, Zonghui Ji, Zhi’he Dou

Producing Pure Magnesium Through Silicothermic Under the Atmospheric Pressure

TheAtmospheric pressure majority of pure magnesiumMagnesium produced worldwide is made by using silicothermicSilicothermic method (Pidgeon processPidgeon process). However, the Pidgeon processPidgeon process suffers poor efficiency, low industrial concentration, and intermittent production. The main reason is that Pidgeon processPidgeon process requires to keep the reaction chamber in a vacuum state during the entire reduction process. By analyzing the thermodynamic reaction principle, we reveal that it is the low magnesiumMagnesium partial pressure instead of vacuum that is necessary for the silicothermic processSilicothermic process. Based on this understanding, we develop a new technique that can produce pure magnesiumMagnesium under the atmospheric pressureAtmospheric pressure by using silicothermicSilicothermic method. Flowing argonFlowing argon is used to carry away the magnesium vaporMagnesium vapor around the reactants, which reduces the local magnesiumMagnesium partial pressure. The magnesiumMagnesium production efficiency reaches 82.36% that is comparable to the widely used Pidgeon method, and high purityHigh purity of magnesiumMagnesium with 99.97 wt% after melting is produced directly. The industrialized application of this exciting technique is expected to help the silicothermicSilicothermic to realize high efficiency, automated, and continuous production while at the same time completely change the poor production conditions, and reduce energy consumption and pollution.

Fei Liu, Bo Yang, Bo-Yu Liu, Jiao Li, Zhi-Min Chang, Zhi-Wei Shan

Effect of Temperature on Magnesium Vapor Condensation in Inert Carrier Gas

The process of magnesiumMagnesium extraction by silicothermic processSilicothermic process is in vacuum, which leads to discontinuous production. The condensation of magnesium vaporMagnesium vapor in inert gasInert gas is an important step to realize continuous magnesiumMagnesium production. In this paper, the condensation behavior of magnesium vaporMagnesium vapor in inert carrier gas is studied. The effects of temperatures on the condensation phenomenon, temperature in condensation zone, direct recovery rate of condensation, and microstructureMicrostructure of magnesium vaporMagnesium vapor were investigated. The results show that three different condensation appearance can be obtained by magnesiumMagnesium condensation in argon gas conditions, and the size has significant difference, and large particles of condensed magnesiumMagnesium are more than 500 μm, small particles of magnesiumMagnesium from 50 to 100 μm and powdered magnesiumMagnesium less than 10 μm. With the increase of temperature, the initial condensation temperatureInitial condensation temperature of magnesium vaporMagnesium vapor increases from 680.2 to 745.1 °C, small particles of magnesiumMagnesium increases, while the powdered magnesiumMagnesium keeps constant; the direct recovery rate of large particles of magnesiumMagnesium decreases from 27.1 to 15.4%, and the direct recovery rate of condensed magnesiumMagnesium of small particles increases; higher purity of magnesiumMagnesium can be obtained at different temperatures, which can provide theoretical support for continuous magnesiumMagnesium production process.

Jibiao Han, Ting’an Zhang, Daxue Fu, Junhua Guo, Zonghui Ji, Zhihe Dou

Fundamentals, Mechanical Behavior, Twinning, Plasticity, and Texture II

Frontmatter

Mapping Anisotropy and Triaxiality Effects in Magnesium Alloys

MicrostructureMicrostructure , materialAnisotropy properties, and macroscopic stress state closely interact in determining the strength and fracture resistance of ductile metals. While a fair understanding of the microstructureMicrostructure -stress interaction on strength, deformationDeformation stability, and damage has been achieved for common engineering alloys, the same is not true for magnesiumMagnesium (Mg) alloys. A fundamental understanding of how the net plastic anisotropyPlastic anisotropy influences the macroscopic load-deformationDeformation characteristics and deformationDeformation stability will potentially aid the development of high-performanceMagnesium alloy (Mg alloy) Mg alloysMagnesium alloy (Mg alloy) . A concerted multi-scale computational effort is essential in providing a deeper understanding of the deformationDeformation micromechanicsMicromechanics of Mg alloysMagnesium alloy (Mg alloy) . In this paper, we investigate the microstructureMicrostructure -property linkages under tensile and compressive loading states through high-fidelity crystal plasticityCrystal plasticity modeling and simulation. Extended investigations along this path should enable the development of guidelines for damage-tolerant design of Mg alloysMagnesium alloy (Mg alloy) .

Padmeya P. Indurkar, Shahmeer Baweja, Robert Perez, Amol Vuppuluri, Shailendra P. Joshi

Cold Formability of Extruded Magnesium Bands

Three magnesium alloysMagnesium alloy (Mg alloy) with textureTexture and microstructureMicrostructure modifying elements, binary M2, and the alloyed counterparts with Ca (MX21) and rare earthRare earth element (ME21) were extruded to flat bands under similar conditions. The microstructureMicrostructure and textureTexture in extrusionExtrusion significantly differ from those developed in rolled magnesiumMagnesium sheets. The influence on the mechanical propertiesMechanical properties and the forming behaviour, in terms of Erichsen values, with relation to microstructureMicrostructure, textureTexture, and strain rate sensitivity was examined. A clear difference in textureTexture development and strain rate sensitivity is shown in dependence on the alloying composition. In addition, not only the textureTexture, but also the microstructureMicrostructure has a great influence on formabilityFormability.

Maria Nienaber, Jan Bohlen, Jose Victoria-Hernández, Sangbong Yi, Karl Ulrich Kainer, Dietmar Letzig

The Effect of Plastic Deformation on the Precipitation Hardening Behavior of Biodegradable Mg–Sr–Ca–Zn Based Alloys

In this study, the precipitationPrecipitation hardening behaviour of Mg–Sr–Ca–Zn based alloyAlloy system with trace additions was investigated. The as-cast microstructureAs-cast microstructure was found to be composed of Mg2(Ca, Sr) interdendritic phases surrounding the α-Mg matrix. The effect of temperature as well as initial plastic deformationDeformation on the precipitationPrecipitation hardening behaviour was analyzed via ageing treatments. More effective age-hardening response was achieved via ageing at 150 °C both in as-cast and deformed samples. Prior plastic deformationDeformation resulted in changes in precipitationPrecipitation kinetics.

Matteo Nicolosi, Baoqi Guo, Mihriban Pekguleryuz, Mert Celikin

Experimental Investigation of Raster Tool Path Strategy for Friction Stir Processing of Magnesium Alloy

Friction stir processingFriction Stir Processing (FSP) is an emerging method for refining the grain structure of the metals. Single pass friction stir processing of magnesiumMagnesium alloys has been reported in the literature, and very few works address the multi-pass friction stir processingFriction Stir Processing (FSP). However, most of the studies are limited to a very small region and do not show the properties of complete processed blank. In the present work, a raster tool path strategy is adopted to modify the microstructure of the as-cast magnesiumMagnesium alloy. The tool rotation direction and tool shoulder overlap are varied to process the magnesiumMagnesium samples. The microstructural evolution of the processed samples is investigated. Experimental observations show that raster scan parameters significantly affect the microstructural variation within each sample and across the samples. Based on the findings, a raster tool path strategy is proposed for grain refinement without any defectDefects in the processed region.

Abhishek Kumar, Nikhil Gotawala, Aarush Sood, Sushil Mishra, Amber Shrivastava

Quantitative Relationship Analysis of Mechanical Properties with Microstructure and Texture Evolution in AZ Series Alloys

The present study investigated the correlation between microstructureMicrostructure, textureTexture, and mechanical propertiesMechanical properties of AZ31 sheets. In magnesium alloysMagnesium alloy (Mg alloy), microstructural and textureTexture factors have a decisive influence on mechanical propertiesMechanical properties due to their specific c/a ratios for hexagonal close-packed structure. It is well known that the yield strengths of Mg alloysMagnesium alloy (Mg alloy) are followed by the Hall–Petch relation. Nevertheless, AZ-based sheets with relatively large grain size exhibit higher yield strength than those with finer microstructureMicrostructure. This is mainly due to the textureTexture strengthening. For this reason, there is an increasing need to quantify the contribution of textureTexture and microstructureMicrostructure to mechanical propertiesMechanical properties in Mg alloysMagnesium alloy (Mg alloy). A multiple regression analysisMultiple regression analysis is conducted to explore the quantitative correlation of the mechanical propertiesMechanical properties with the microstructureMicrostructure and textureTexture factors, such as grain size, phase fraction of secondary particles, maximum intensity of basal poles, and Schmid factor for basal $$ $$ < a > $$ $$ slip. This study focuses on evaluating quantitatively the relative weights of microstructureMicrostructure and texture evolutionTexture evolution such as grain refinementGrain refinement and texture weakeningTexture weakening, when determining yield strength depending on loading direction at room temperature.

Joung Sik Suh, Byeong-Chan Suh, Jun Ho Bae, Sang Eun Lee, Byoung-Gi Moon, Young Min Kim

On the Influence of Twinning and Detwinning on the Deformation of Mg at the Micron Scale

The influence of twinningTwinning and detwinning on the constitutive mechanical response of Mg was investigated via microcompression tests of single-crystalline pillars of nominal [0001] and [10-10] orientations, and bicrystalline pillars containing a single $$ \left\{ {1 0 \overline{1} 2} \right\} $$ twin boundary. The [0001] pillars exhibit the highest initial yield strength while the [10-10] and bicrystalline pillars initially yield at significantly lower stress, at which twin nucleation and growthNucleation and growth or migration commence. Depending on the extent of straining, the [10-10] and bicrystalline pillars exhibit a secondary yield point associated with the deformationDeformation of the newly formed [0001] oriented pillar. The mechanical results point to an anisotropyAnisotropy in the mechanical consequence of twin motion, as characterized through the comparison of the three micropillar orientations; a twin-mediated hardening is indicated by the relative stress-strain behavior.

Mohammadhadi Maghsoudi, Gyuseok Kim, Markus Ziehmer, Erica T. Lilleodden

An Investigation on the Microstructure and Mechanical Properties of the Hot-Dip-Aluminized-Q235/AZ91D Bimetallic Material Produced by Solid–Liquid Compound Casting

TheSolid–liquid compound casting hot-dip-aluminized-Q235/AZ91D bimetallic material was acquired by casting the melted magnesium alloyMagnesium alloy (Mg alloy) into the mould where the hot-dip-aluminized-Q235 had been inserted to achieve the lightweight with optimal mechanical propertiesMechanical properties . The microstructureMicrostructure and mechanical propertiesMechanical properties of the hot-dip-aluminized-Q235/AZ91D was investigated in this study. The results revealed that the metallurgical reaction in the interface zone which could be divided into two different layers was formed between Q235 and AZ91D. The layer close to AZ91D was composed of MgAl2O4 and Al12Mg17, and the layer adjacent to Q235 was comprised of FeAl3. What’s more, the average microhardness of the interface zoneMicrohardness of the interface zone was higher than AZ91D substrate and Q235. Moreover, the average microhardness of the layer close to Q235 (469.6HV) was much higher than the layer adjacent to AZ91D (136HV) due to the generation of FeAl3 and MgAl2O4. In addition, the shear strengthShear strength of Q235/AZ91D was about 8.22 MPa.

Jun Cheng, Jian-hua Zhao, Yao Tang, Jing-jing Shang-guan

Poster Session

Frontmatter

Effect of Zinc on Solidification and Aging Behaviour of Magnesium Alloys Containing Rare Earths

Magnesium sheetMagnesium sheet continuously creates a great interest with potentials in a wide range of technically advanced applications. The interest was initially driven by a reduction in fuel consumption within transportation sectors and was later expanded to consumer electronic housings, components in electrification of vehicles, and aerospace applications. In a search for alloys with suitable formabilityFormability , a particular attention is paid to Mg–ZnMg-Zn –RE (rare earthRare earth ) grades. It is known that the presence of Zn in binary Mg–ZnMg-Zn alloys leads to enhanced strength and ductility. However, the effect of Zn on alloyAlloy formabilityFormability in the presence of rare earths is less pronounced. In this report, the solidification and aging behavior of Mg–xZn–1Nd (x = 1, 2, 4 wt%) alloys are described. To analyze the phase nucleation and growthNucleation and growth during melting and solidification, the Universal Metallurgical Simulator and Analyzer (UMSA) was used. Hardness values of Mg–ZnMg-Zn –Nd alloys increased with increasing Zn contents both in as-cast and after heat treatments with changes being accompanied by the alloyAlloy structure refinement. The results are discussed in terms of the role Zn plays in properties of magnesium alloysMagnesium alloy (Mg alloy) containing rare earths. Increasing Zn content in the Mg-xZn-1Nd alloyAlloy sheets led to a moderate increase in ultimate tensile strength and yield stress but substantial reduction in ductility.

A. Javaid, F. Czerwinski

Influence of Manganese on Deformation Behavior of Magnesium Under Dynamic Loading

Magnesium alloysMagnesium alloy (Mg alloy) areMagnesium promising lightweight structural materialsMaterials . However, their practical utilization requires improvement of strength and ductility. Adding manganese as a solute improves the room-temperature ductility of magnesium alloysMagnesium alloy (Mg alloy) by facilitating grain boundary sliding, but its effects on deformation behaviorDeformation behavior under dynamic loading remain unclear. Accordingly, we investigated the strain rate dependenceStrain rate dependence of both the flow stress and the deformation mechanismDeformation mechanism of Mg–Mn alloys via tensile tests over a wide range of strain rates. Grain boundary sliding induced relatively larger elongation under quasi-static conditions. On the contrary, the Mg–Mn alloyAlloy exhibited limited necking in the high strain rate regime dominated by intergranular fracture.

Ryutaro Goeda, Masatake Yamaguchi, Tatsuya Nakatsuji, Naoko Ikeo, Toshiji Mukai

Microstructure and Hardness of Porous Magnesium Processed by Powder Metallurgy Using Polystyrene as the Space Holder

Porous magnesiumPorous magnesium (Mg)Microstructure withPowder metallurgy differentPolystyrene overall porosities (4.1 ± 0.5, 6.1 ± 1.3,12.9 ± 3.3, and 19.0 ± 6.2%) were manufactured by powder metallurgyPowder metallurgy using polystyrenePolystyrene (PS) as the space holder. The samples were either hot pressed or cold pressed. Two types of PS were used to study the effect of molecular weight (Mw) of polymer space holder on properties of porous Mg. Porous Mg contained small amount of MgO. The utilization of lower Mw PS as the space holder introduced less amount of MgO into porous Mg. Average pore size increased from 2.0 ± 0.03 to 7.9 ± 3.3 µm with overall porosity increasing from 4.1 ± 0.5 to 19.0 ± 6.2%. Hardness of porous Mg decreased with overall porosity increasing. Using PS as the space holder, porous Mg by hot pressing route exhibited higher hardness than that by cold pressing route.

Ning Zou, Qizhen Li

Backmatter

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