Basal Texture Rotation Induced by the Coupling Effect of Grain Boundary Sliding and Shear Strain

Abstract

Basal texture directional rotation, the c-axes of grains align parallel to the arcuate streamline, occurs during the hot extrusion process. Microstructures in one arcuate region along the streamline direction revealed low grain orientation spread values, fine equiaxed grains, and an almost unchanged texture intensity. These unusual microstructures indicate that this texture rotation is not caused by intragranular dislocation slips but rather by grain boundary sliding (GBS). The GBS originates from the lower strength near grain boundaries than grains, allowing grain boundaries to accommodate a significant portion of the deformation. This microstructure, featuring hard grains and soft grain boundaries, is analogous to a system of hard particles suspended in viscous fluid. According to this analogy, the shear strain in the extrusion process drives the directional rotation of grains surrounded by grain boundaries like hard particles. Therefore, this basal texture rotation is attributed to the coupling effect of GBS and shear strain.

Keywords: Magnesium alloys, Extrusion, Grain boundary sliding, Texture, Streamline direction