Magnesium Technology 2021: Mechanical Behavior
Sponsored by: TMS Light Metals Division, TMS: Magnesium Committee
Program Organizers: Victoria Miller, University of Florida; Petra Maier, University of Applied Sciences Stralsund; J. Brian Jordon, Baylor University; Neale Neelameggham, IND LLC
Wednesday 8:30 AM
March 17, 2021
Room: RM 31
Location: TMS2021 Virtual
Session Chair: Brian Jordon, University of Alabama; Kiran Solanki, Arizona State University
8:30 AM Invited
Quasi-static and Dynamic Rate Mechanical Behavior and Microstructural Investigation of High-purity Mg and AZ31B Alloy: Benjamin Morrow1; Ellen Cerreta1; Saryu Fensin1; Sara Perez-Bergquist1; Carl Trujillo1; Suveen Mathaudhu2; Veronica Anghel1; Rodney McCabe1; George Gray1; 1Los Alamos National Laboratory; 2University of California - Riverside
High-purity Mg and Mg AZ31B alloy were tested under quasi-static and dynamic strain rate conditions to examine the evolution of microstructure during deformation. EBSD is used to quantify the relative activity of mechanisms under various loading conditions, especially with respect to slip and twinning. Orientation had a large effect on strain rate sensitivity and twinning activity in both pure and alloyed Mg. Samples were also tested in a shear-loading configuration to examine microstructural evolution under these conditions. Adiabatic shear bands were not observed in high-purity Mg specimens. Deformation bands were observed in AZ31B, though slip was the dominant mechanism, likely due to adiabatic heating during deformation. Additionally, several efforts have used in situ straining TEM, and HRTEM to study individual defects and defect interactions during and after deformation (especially twin-twin and twin-dislocation) at the nano-scale, which can have a considerable effect on both dislocation and twin mobility.
9:00 AM Invited
Understanding Twinning: Detwinning Behavior of Unalloyed Mg during Low-cycle Fatigue Using High Energy X-ray Diffraction: Aeriel Murphy-Leonard1; John Allison2; 1Naval Research Laboratory; 2University of Michigan
The influence of grain size and alloying on cyclic stress-strain(CSS) and low cycle fatigue (LCF) behavior in magnesium was investigated using strain-controlled, fully-reversed LCF conditions. The initial texture was so that the c-axis of most grains was normal to the loading direction to promote extension twinning during compression and the removal of those twinned regions during tension of the following cycle. In both pure Mg and Mg-4Al a tension-compression asymmetry was observed and related to twinning and detwinning. The loop shape asymmetry increased with strain amplitudes in both materials. Interactions between solutes, twins, and dislocations leads to higher hardening rate in the Mg-4Al when compared to the unalloyed condition. Electron back scatter diffraction (EBSD) analysis revealed that twin activity reoccurred at the same locations after successive cycling. EBSD analysis also showed that residual twins remain in the fine-grained pure Mg condition after 104 cycles.
9:30 AM
The Effects of Basal and Prismatic Precipitates on Deformation Twinning in AZ91 Magnesium Alloy: Brandon Leu1; M Arul Kumar2; Irene Beyerlein1; 1University of California Santa Barbara; 2Los Alamos National Laboratory
The advancement of Mg technologies is motivated by inherently high specific-strength and low-density of Mg and its alloys. For example, the AZ91 is a popular cast Mg alloy due to its relatively high strength, excellent corrosion resistance and castability. However, these Mg alloys have not yet seen widespread application due to their poor formability and twinning behavior. Understanding twinning deformation is critical in emerging Mg technology since twinning can strongly influence the ductility and stability of those materials. In particular, the interactions between twins and β-phase precipitates in AZ91 Mg-alloys are important since both twins and precipitates readily form in these alloys. In this study, we use elasto-viscoplastic fast-fourier-transform (EVP-FFT) crystal plasticity modeling to explore the interactions between twin and precipitates found in AZ91 Mg-alloys. Twin propagation, transmission across precipitates, and engulfment around precipitates will be investigated to gain a clearer understanding of how they influence twin development.
9:50 AM
On the Role of Crystallographic Anisotropy and Texture in Damage Tolerance of Magnesium and its Alloys: Shahmeer Baweja1; Padmeya Indurkar2; Shailendra Joshi1; 1University of Houston; 2National University of Singapore
The crystallographic plastic anisotropy and the asymmetry of magnesium reflect in its polycrystal response via texture. While texture-strength linkages have been studied, the role of textural variability on damage remains elusive. To that end, metrics are needed to relate plastic anisotropy to damage, which is challenging. A possible approach is to adopt mechanistic descriptions of the damage. In this work, we adopt the following approach: we appeal to the Hill anisotropy tensor as a potential damage descriptor. First, extensive 3D crystal plasticity simulations are performed for a wide range of textures. The resulting responses are used to obtain the Hill coefficients, which are used in projecting the propensity of textured polycrystals to damage by: (i) void evolution, or (ii) shear instability. A focus is on understanding the potential roles textural variability and crystallographic plastic anisotropy play in damage under different loading conditions.
10:10 AM Invited
Achieving Excellent Room Temperature Formability and High Strength in Wrought Magnesium Alloy Sheets: Taisuke Sasaki1; Zehao Li1; Kazuhiro Hono1; 1NIMS
Precipitation hardenable magnesium alloy is promising to overcome the strength-formability dilemma as demonstrated in a recently developed bake-hardenable Mg-Al-Zn-Ca-Mn alloy, which exhibits comparable room temperature formability and strength with 6XXX series aluminum alloys. This presentation will discuss strategies to realize the excellent room temperature formability and the high strength in magnesium alloy sheets. The addition of Zn plays a critical role in achieving good room temperature formability in Mg-Ca-Al alloy by texture weakening. The weakened texture is attributed to the nucleation of weakly textured grains along twin boundaries during the solution treatment. The Zn content should be optimized to achieve satisfactory bake-hardenability. A systematic study shows that the bake-hardenability is a unique feature observed in the dilute magnesium alloys strengthened by the precipitation of Guinier Preston (G.P.) zones. Therefore, the precipitation hardenable dilute Mg-Zn-Ca alloy would open up a possibility to broaden the application of wrought magnesium alloys.
10:40 AM Invited
Texture and Microstructure Evolution in Thermomechanically Processed Mg-Ca and Mg-Zn-Ca Alloys: Tracy Berman1; John Allison1; 1University of Michigan
Mg-Zn-Ca alloys have the potential for producing Mg alloy sheets with weaker basal textures and therefore improved formability. Thermomechanical processing (TMP) also plays a substantial role in determining the final sheet texture. The interplay of these variables, TMP and alloying, complicates comparisons of alloys across the literature. This work systematically explores the texture evolution and recrystallization behavior in Mg-Ca and Mg-Zn-Ca alloys during plane strain compression (PSC) using a Gleeble thermomechanical simulator. It is demonstrated that the basal texture intensity and texture characteristics change significantly during post-deformation annealing, particularly in the ternary alloys. It is also shown that careful selection of the TMP processing variables used during PSC is essential to producing weak textures. In particular, it is important to limit the recrystallization that occurs between compressive hits. This is achieved by adjusting solute content, strain rate, and the duration of the soak between passes.
11:10 AM
Eliminating Yield Anisotropy and Enhancing Ductility in Mg Alloys by Shear Assisted Processing and Extrusion: Dalong Zhang1; Jens Darsell1; Nicole Overman1; Darrell Herling1; Vineet Joshi1; 1Pacific Northwest National Laboratory
Solid phase processing techniques such as friction stir welding, Shear assisted processing and extrusion (ShAPE)/ friction extrusion and cold spray have been successfully demonstrated as promising thermomechanical methods to produce metallic materials with enhanced performance. In this study, AZ series with and without silicon, ZK60 Mg alloys in as-received forms (as-cast or as-extruded) were processed using Shear Assisted Processing and Extrusion (ShAPE). Microstructural characterization was performed using EBSD and TEM and revealed that as compared to the feedstock materials/ billets, friction extruded Mg alloys had more uniform microstructure, equiaxed grains, finer and homogeneously distributed precipitates and chemical homogeneity. It was also observed that basal planes were not oriented parallel to extrusion axis. As a result, rod products exhibited significantly eliminated yield anisotropy and achieved enhanced ductility, which were uncommon or difficult to attain using conventional processing techniques. In addition, modified texture likely suppressed deformation twinning under compressive deformation.
11:30 AM
Numerical Study of Multi-axial Loading Behavior of Mg Alloy AZ31 Extruded Bar: Huamiao Wang1; Xiaodan Zhang1; 1Shanghai Jiao Tong University
Shear strain, coupled with other deformations, is inevitably involved in the forming process with severe plastic deformation. The torsional and torsion-tension coupling behaviors of magnesium alloys are investigated both experimentally and numerically. Rod specimens with different initial textures, prepared from a magnesium alloy AZ31 plate, are tested under the free-end torsion and coupled torsion-tension. Parallelly, the elastic viscoplastic self-consistent model with the twinning and detwinning scheme, in conjunction with a torsion-specific finite element approach, is employed to model the free-end torsion, fixed-end torsion, and coupled torsion-tension. The anisotropic torsional and torsion-tension coupling behaviors are captured by the model. The Swift effect, which is picky on the constitutive model, is also reproduced by the model. Furthermore, the torsional and torsion-tension coupling behaviors of magnesium alloys are understood in terms of the deformation textures, relative activities of deformation mechanisms, and the distributions of the stress, strain, twin volume fraction.