Ultrasonic vibration-assisted tube extrusion shear expansion (UVaTESE): A novel process to manipulate the texture of AZ31 magnesium alloy

Abstract

AZ31 magnesium (Mg) alloy prepared via the extrusion process forms an immensely strong {0001} basal texture, therefore there is a necessity to improve the existing extrusion process to achieve a weakening of the {0001} basal texture of the AZ31 Mg alloy. In this study, a novel process called UVaTESE is proposed. The Mg alloy texture and slip system activation at four ultrasonic vibration (UV) frequencies have been simulated via ABAQUS-VUMAT and VPSC, individually. The simulation results indicate that UV is capable of diffusing the {0001} basal texture of the Mg alloy along the extrusion direction (ED) and transverse direction (TD) and significantly improves the activation of pyramidal slip <c+a>. The simulations are verified experimentally, and the {0001} basal texture of AZ31 Mg alloy has the identical tendency to disperse along ED and TD. Prismatic slip <a> and pyramidal slip <c+a> jointly lead to diffusion of the grain basal texture along the TD, while grains with basal texture diffused along the ED are controlled by both basal slip <a> and pyramidal slip <c+a>. UV has a positive effect on the grain refinement as well as on the homogeneity of AZ31 Mg alloy. The proportion of dynamic recrystallization (DRX) of AZ31 Mg alloy is proportional to the frequency of UV, and it is noteworthy that the mechanism of DRX behavior is not affected by UV. This novel process provides a fundamentally innovative approach to the preparation of Mg alloys and magnesium-aluminum (Mg-Al) composite tubes via extrusion.