Ex-situ EBSD investigation of the reduced c/a values and work hardening behavior in Mg-4Li-1Al-0.5Y alloy under hot compression

Abstract

The microstructural and textural evolution of the annealed Mg-4.26 wt% Li-1.05 wt% Al-0.52 wt% Y (denoted as Mg-4Li-1Al-0.5Y) alloy at 200 °C and strain rate of 0.1 s-1 was investigated via ex-situ electron backscatter diffraction (EBSD). Microstructural analysis revealed that the axial ratio (c/a) of the annealed Mg-4Li-1Al-0.5Y alloy decreased to 1.605, which reduced the critical shear stress (CRSS) of non-basal slip and promoted the activation of pyramidal <c + a> slip in the early stage of deformation (ε = 0.02). In addition, a weak {112‾0} prismatic texture was formed in the investigated alloy, and the hot compression curve exhibited a significant work-hardening characteristic with a yield strength of 92 MPa. As the strain increased, the texture strength gradually decreased, and the number of low-angle grain boundaries (LAGBs) increased. In addition, the area fraction of {101‾2} extension twins decreased, while no {101‾1} compression twins or {101‾1}-{101‾2} double twins were observed. Moreover, the high dislocation activities indicated that the decrease in the axial ratio (c/a) promoted the non-basal slip more actively and inhibited the activity of the twins to some extent, which resulted in significant work hardening of the Mg-4Li-1Al-0.5Y alloy during the compression process.