Texture Weakening and Grain Refinement by High Speed Rolling and Annealing of an AZ31 Magnesium Alloy

High-speed rolling of 1000 m/min has been used to produce Mg AZ31 alloy sheets at an initial temperature of 100 degrees C with increasing reductions to generate different as-rolled microstructures. After a reduction of 30%, a heavily twinned and shear-banded microstructure was seen, while after a reduction of 49%, a partially dynamically recrystallized (DRXed) and twinned microstructure was observed. The as-rolled specimens were then annealed at temperatures from 200 to 500 degrees C. Texture weakening and grain refinement were achieved at both reductions during annealing by static recrystallization (SRX). However, the 49% reduction specimen showed a much higher kinetics of SRX and a higher rate of texture weakening, comparing to the 30% reduction specimen. The weakest texture achieved in the former was slightly lower than that in the latter, which indicates that texture weakening is more effective in the specimen with heavily twinned and shear-banded microstructure than that with partially DRXed and twinned microstructure. Nevertheless, the average size of the SRXed grains at the full recrystallization condition of the specimen after the reduction of 49% was only half of that after 30%.