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1. Strain partitioning-induced anisotropy in thermomechanically processed magnesium alloys comprised of earth-abundant elements

   https://doi.org/10.1016/j.scriptamat.2025.116659  

   Bhattacharyya, Jishnu J; Faberman, Seth; Sullivan, Aaron; Saha, Mainak; Sasaki, Taisuke; Agnew, Sean R (June 2025, Scripta Materialia)

   Dilute Mg alloys based upon earth-abundant elements, e.g., Al, Ca, and Zn have attractive combinations of strength, ductility, and workability. Even higher strength can be obtained in work-hardened material without the heat treatments required to induce Guinier-Preston zone strengthening of previously studied versions of these alloys. This stems from a slightly stronger crystallographic texture than is present after solutionizing, a high dislocation density, and to a lesser degree, a fine distribution of globular Zn-rich precipitates. The anisotropic plastic response of sheet material is described using an elasto-viscoplastic self-consistent (EVPSC) polycrystal model. Strain partitioning between grains during rolling-induced strain hardening is held responsible for the yield strength, ductility, and especially, strain hardening anisotropy. Texture-induced plastic anisotropy is well- known, but the effect of strong partitioning of strain between variously oriented grains is critical to explain what may be classified as a sort of strain path change (generalized Bauschinger) effect. 

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2. Revisited precipitation process in dilute Mg-Ca-Zn alloys

   https://doi.org/10.1016/j.actamat.2023.119072  

   Li, Z.H.; Cheng, D.; Wang, K.; Hoglund, E.R.; Howe, J.M.; Zhou, B.C.; Sasaki, T.T.; Ohkubo, T.; Hono, K. (September 2023, Acta Materialia)

   To obtain thorough understandings of precipitation process in heat-treatable Mg-Ca-Zn alloy, we revisited the precipitation process of a Mg-0.3Ca-0.6 Zn (at.%) dilute alloy during isothermal aging at 200 °C using an aberration-corrected scanning transmission electron microscope, atom probe tomography, and first-principles calculations. The monolayer G.P. zones form on the (0002)α plane in the peak-aged condition and transform into tri-atomic layer η'' and η' plates with a thickness of a single unit-cell height. The η' plates, then, form in pairs and stacks with energetically favorable 4–5 atomic layers of pure magnesium between the plates. While such a transformation path is similar to that seen in Mg-RE-Zn alloys (RE: rare-earth elements), the unique structure of coarse η1 plates that precipitate after the η' plates leads to a different precipitate microstructure evolution from the Mg-RE-Zn system. The η1 phase (Mg7Ca2Zn3) is unevenly distributed in the matrix after 100 h of aging and finally evolves to the equilibrium η phase (Mg10Ca3Zn6) phase with a hexagonal structure. First-principles calculations of energetics were performed to further identify the crystal structure and stability of the precipitates, supporting the following new precipitation sequence: S.S.S.S. → G.P. zones → η'' → η' → η' pairs and stacks / η1 → η 

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3. Adjustment of the Mechanical Properties of Mg2Nd and Mg2Yb by Optimizing Their Microstructures

   https://doi.org/10.3390/met11030377  

   Schmidt, Jonas; Beyerlein, Irene J.; Knezevic, Marko; Reimers, Walter (March 2021, Metals)

   null (Ed.)

   The deformation behavior of the extruded magnesium alloys Mg2Nd and Mg2Yb was investigated at room temperature. By using in situ energy-dispersive synchrotron X-ray diffraction compression and tensile tests, accompanied by Elasto-Plastic Self-Consistent (EPSC) modeling, the differences in the active deformation systems were analyzed. Both alloying elements change and weaken the extrusion texture and form precipitates during extrusion and subsequent heat treatments relative to common Mg alloys. By varying the extrusion parameters and subsequent heat treatment, the strengths and ductility can be adjusted over a wide range while still maintaining a strength differential effect (SDE) of close to zero. Remarkably, the compressive and tensile yield strengths are similar and there is no mechanical anisotropy when comparing tensile and compressive deformation, which is desirable for industrial applications. Uncommon for Mg alloys, Mg2Nd shows a low tensile twinning activity during compression tests. We show that heat treatments promote the nucleation and growth of precipitates and increase the yield strengths isotopically up to 200 MPa. The anisotropy of the yield strength is reduced to a minimum and elongations to failure of about 0.2 are still achieved. At lower strengths, elongations to failure of up to 0.41 are reached. In the Mg2Yb alloy, adjusting the extrusion parameters enhances the rare-earth texture and reduces the grain size. Excessive deformation twinning is, however, observed, but despite this the SDE is still minimized. 

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4. First-Principles Investigation of the Early-Stage Precipitations in Mg-Sn and Mg-Zn Alloys

   Cheng, D.; Wang, K.; Zhou, BC. (February 2022, Magnesium Technology)

   Maier, P.; Barela, S.; Miller, V.M.; Neelameggham, N.R. (Ed.)

   Mg-Sn and Mg-Zn alloys exhibit a strong age-hardening effect and have become promising bases for high-strength and low-cost Mg alloys. However, the atomic structures and phase stabilities of various precipitates and intermetallic compounds during the heat treatment in these systems remain unclear. Here we use a combined approach of first-principles calculations and cluster expansion (CE) to investigate the atomic structures and thermodynamic stabilities of the experimentally reported precipitates as well as orderings on the FCC and HCP lattices in Mg-Sn and Mg-Zn alloys. From the low energy structures searched by CE, potential Guinier–Preston (GP) zones are identified from preferred HCP orderings. The slow convergence for CE of HCP Mg-Zn, compared with that of Mg-Sn system, is attributed to the long-ranged interactions resulting from the larger lattice mismatch. This study could help design better age-hardened Mg alloys. 

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5. Influence of chemical heterogeneity and microstructure on the corrosion resistance of biodegradable WE43 magnesium alloys

   https://doi.org/10.1039/c9tb00388f  

   Mraied, Hesham; Wang, Wenbo; Cai, Wenjun (October 2019, Journal of Materials Chemistry B)

   null (Ed.)

   Magnesium–yttrium-rare earth element alloys such as WE43 are potential candidates for future bioabsorbable orthopedic implant materials due to their biocompatibility, mechanical properties similar to human bone, and the ability to completely degrade in vivo . Unfortunately, the high corrosion rate of WE43 Mg alloys in physiological environments and subsequent loss of structural integrity limit the wide applications of these materials. In this study, the effect of chemical heterogeneity and microstructure on the corrosion resistance of two alloys with different metallurgical states was investigated: cast (as in traditional preparation) and as-deposited produced by magnetron sputtering. The corrosion behavior was studied by potentiodynamic polarization and electrochemical impedance spectroscopy tests in blood bank buffered saline solution. It was found that the as-deposited alloy showed more than one order of magnitude reduction in corrosion current density compared to the cast alloy, owing to the elimination of micro-galvanic coupling between the Mg matrix and the precipitates. The microstructure and formation mechanism of corrosion products formed on both alloys were discussed based on immersion tests and direct measurements of X-ray photoelectron spectrometry (XPS) and cross-sectional transmission electron microscopy (TEM) analysis. 

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