Microstructure, texture evolution and mechanical anisotropy of Mg-Gd-Y-Zn-Zr alloy sheets produced by unidirectional and cross rolling

Abstract

The unidirectional rolling (UR) and cross rolling (CR) were used to process the Mg-4.7Gd-3.4Y-1.2Zn-0.5Zr (wt.%) alloy sheets. The effect of rolling routes on microstructure, texture evolution, and mechanical anisotropy was investigated. The deformed grains in UR alloy were gradually elongated along the RD, and the intragranular lamellar LPSO phase also transforms into a rod-shaped structure during rolling. For CR alloy, the occurrence of dynamic recovery results in the LPSO phase remaining lamellar shape during rolling, and the deformed grains are rounder than those in UR alloy. After rolling, UR alloy exhibits a texture with basal pole deviates from ND toward the location between TD and RD, which is caused by the synergistic effect of limited twinning, basal and prismatic slip. The CR alloy shows a texture with basal poles deviating from ND to RD 15.6°, which results from the activation of basal slip, pyramidal slip, and multiple twinning variants. The UR alloy exhibits approximately isotropic in yield strength and anisotropy in elongation, while the CR alloy presents a completely different result. The anisotropy in yield strength of CR alloys is related to their texture distribution and remarkably different basal slip Schmid factor in three tensile directions. The isotropic in elongation of CR alloys can be explained by the distribution frequency of tilt angles between basal poles and tensile directions, as well as the kink deformation of lamellar LPSO phase.