Study on mechanical behaviors and theoretical critical shear strength of cold-rolled AZ31 alloy with different Li additions

Abstract

The as-extruded Mg-xLi-3Al-1Zn (x = 1, 3, 5; wt%) sheets (LAZ131, LAZ331 and LAZ531 respectively) were performed with different reductions in multi-pass cold-rolling process. The changed mechanical behaviors of cold-rolled AZ31 alloys with Li additions were investigated via the electron-backscattered diffraction (EBSD) and texture. The results indicated that the main deformation modes of LAZ131 alloy were twinning and basal slip during cold rolling process. However, for the LAZ331 and LAZ531 alloy, the prismatic slip, {112̅2} pyramidal slip, {101̅2} extension twining, {101̅1} contraction twinning sequentially dominated in the deformation with increased rolling reduction. Then, the theoretical critical shear strength (τmax) (reflecting the critical resolved shear stress, CRSS) of Mg and Mg-Li crystal was characterized by first-principles calculation. The direct consequences from calculations indicated that the value ofτmax decreased from 1571 MPa to 1276 MPa in pyramidal slip systems, while that increased from 114 MPa to 177 MPa in basal slip, due to doping Li to Mg single crystal. The decrease in τmax ratio between non-basal and basal may promote an easy activation of non-basal slip and show different deformation modes of cold-rolled AZ31 alloys with different Li additions.