Effect of Stress State on Plastic Behavior, Deformation Mechanism and Texture Evolution of an Mg-Gd-Y Alloy: Experiment and Multi-Scale Simulation

Abstract

This research investigates the effect of stress states on the plastic behavior of an Mg-Gd-Y alloy by mechanical tests and numerical simulation both in macroscopic and microscopic scales. Experiments were carried out under distinct stress states including tension, compression and shear, to uncover the stress state-dependent deformation behavior of the Mg-Gd-Y alloy. The stress-state dependent plastic deformation was numerically simulated by the established Cazacu-Barlat’2004+Swift-Voce constitutive model. The initial texture was measured by the electron backscatter diffraction (EBSD) technology. The material constants of the visco-plastic self-consistent equation with the predominant twin re-orientation (VPSC-PTR) model were calibrated optimally based on a developed experiment-inverse engineering (I-E) method with the measured texture. The mechanical experimental result indicates that the Mg-Gd-Y alloy presents an obvious tension-compression asymmetry at the aspect of the yield stress and hardening behavior. The mechanical property is very sensitive for the stress state and loading direction. The EBSD measurement shows that the initial texture belongs to a typical strong basal texture and the axis of great majority grains closes to the normal direction (ND). The predicted deformation behavior by VPSC-PTR matches with experimental results with great accuracy. The VPSC-PTR simulation indicates that the slip systems become the dominant deformation mode as the equivalent strain increases. Through observing the texture evolution, the axis of grains is still along ND under tension condition while the basal poles of grains are reoriented under compression and shear conditions.

Keywords: rare-earth magnesium alloy, strength differential effect, crystal plasticity simulation, deformation mechanism, texture evolution