Ex-situ EBSD analysis of yield asymmetry, texture and twinning development in Mg-5Li-3Al-2Zn alloy during tensile and compressive deformation

In this study, Mg-5Li-3Al-2Zn alloy was successfully fabricated by melting and casting followed by hot extrusion at 573 K. The initial extruded Mg-5Li-3Al-2Zn alloy presented a bimodal structure in which both coarse grains and fine grains coexisted. The asymmetry of tension and compression, texture evolution and twinning types in extruded Mg-5Li-3Al-2Zn alloy during axial tensile and compressive deformations were studied. The experimental results showed that the initial texture component of the extruded Mg-5Li-3Al-2Zn alloy was {0001} basal texture, which led to a strong yield asymmetry of tension and compression (TYS/CYS of 1.46). When the alloy was stretched along the axis, the texture changed little. The main deformation was (10 (1) over bar0) prismatic slip with few {10 (1) over bar2} extension twins produced in some coarse grains, which resulted in weak strain hardening. When the compression was along the axial direction, the initial stage of compressive deformation was dominated by (0001) basal slip. With the increase in strain, large numbers of {10 (1) over bar2} extension twins and few {(1) over bar0 (1) over bar2}-{10 (1) over bar2} double twins were generated in coarse grains. On the other hand, (0001) planes of some fine grains began to rotate and became perpendicular to ED, resulting in the formation of a weak {(1) over bar2 (1) over bar0} texture. With further increase in strain, {0001} basal texture was completely transformed into {(1) over bar2 (1) over bar0} texture. Furthermore, based on theoretical analysis, the extruded Mg-5Li-3Al-2Zn alloy had lower CRSS of prismatic and basal slips compared to other Mg alloys