AZ31 magnesium alloy sheet with high ductility and low anisotropy achieved by a novel asymmetrical angular rolling process

Abstract

The low ductility and strong mechanical anisotropy of wrought magnesium alloys have hindered their further processing and application. In this study, AZ31 magnesium alloy sheet was prepared by a new asymmetrical angular rolling (AAR) process, compared with conventional symmetrical rolling (SR) process and asymmetrical rolling (ASR) process. The effects of three rolling processes on the microstructure, texture and mechanical properties of the alloy sheets were systematically studied. The results show that the AAR sheet exhibits excellent mechanical properties compared to other two rolling processes. It not only achieves the highest ductility of 17.9 %, 17.9 %, and 18.5 % in the three directions, but also has the lowest mechanical anisotropy values for yield strength, ultimate tensile strength and elongation. The AAR process significantly reduces the anisotropy of the material by achieving the smallest average grain size of 4.93 µm and the most homogeneous grain size distribution. Introduced bi-directional asymmetric shear stresses randomizes grain orientation and activates the non-basal slip system, which also significantly reduces the anisotropy. In addition, the tensile twinning mechanism dominates during the AAR process, which contributes to texture weakening and the activation of the non-basal slip system. Through the synergy of these mechanisms, the AAR sheet is characterized by high ductility and low anisotropy.