Magnesium (Mg) alloys typically exhibit anisotropic mechanical behaviors due to their hexagonal close-packed (hcp) crystal structures, often leading to tension-compression asymmetries. Understanding of the asymmetrical and related deformation mechanisms is crucial for their structural applications, particularly in the lightweight transportation industries. Nevertheless, the underlying deformation mechanisms (e.g., slip versus twinning) at each deformation stage during tension and compression have not been fully understood. In this study, we employed tensile and compressive tests on extruded Al and Mn containing Mg alloy, i.e., an AM alloy Mg-0.6Mn-0.5Al-0.5Zn-0.4Ca, during the synchrotron X-ray diffraction. Our results show that distinct deformation behaviors and mechanisms in tension and compression are associated with the strong texture in the extruded samples: (i) The tensile deformation is dominated by dislocation slips, with activation of non-basal 〈a〉 and 〈c + a〉 slip, but deformation twinning is suppressed. (ii) The compressive deformation shows early-stage tensile twinning, followed by dislocation slips. Twinning induces grain reorientation, leading to significant lattice strain evolution aligned with the texture. The pronounced tension-compression asymmetry is attributed to the favorable shear stress direction formed in the twinning system during compression, which facilitates the activation of tensile twins. During tension, the strain hardening rate (SHR) drops significantly after yielding due to limited activated slip systems. In contrast, the samples under compression exhibit significant increases in SHR after yielding. During compression, dislocation multiplication dominates the initial strain hardening, while twinning progressively contributes more significantly than dislocation slip at higher strains. This study improves our understanding of the tension-compression and strain hardening asymmetries in extruded AM Mg alloys.

Refractory high-entropy alloys (HEAs) possess many useful properties such as high strength and high-temperature stability. So far, most studies on refractory HEAs have been limited to a few well-known compositions and on their coarse-grain bulk forms. Here we fabricate nanocrystalline (TiZrHf)_x(NbTa)_1−x HEA thin films with a large range of compositions (x = 0.07–0.90) by the direct current (DC) magnetron co-sputtering technique and measure their mechanical properties using the nanoindentation method. All the as-deposited HEA thin films show a solid-solution body-centered cubic (bcc) structure. As the compositional ratio (x) increases, the elastic modulus decreases from 153 to 123 GPa, following the trend of the rule of mixture. As x increases, the hardness first decreases from 6.5 GPa (x = 0.07) to the lowest value (4.6 GPa, x = 0.48) and then increases to the highest value (7.1 GPa, x = 0.90), showing a concave trend. The change in hardness might be attributed to the combinational influence caused by the atomic size and modulus effects, as well as the texture effect. The authors also propose a few open questions for future studies on this and related HEA systems.