Effect of speed-ratio on microstructure, and mechanical properties of Mg-3Al-1Zn alloy, in differential speed rolling

The effect of speed ratio (SR) in differential speed rolling on the development of texture and microstructure in Mg-3Al-1Zn alloy was systematically investigated in a wide SR range between 1 and 3 at a fixed thickness reduction of 20%. At low SRs, deformation bands and shear bands were dominant. At high SRs >= 2, however, dynamically recrystallized microstructures were developed. The intensity of the basal texture component increased with SR, but decreased to the level of the starting material at high SRs >= 2. The occurrence of the dynamic recrystallization at high SRs was attributed to high-dislocation density accumulation and high temperature rise of a deforming sheet due to large plastic deformation of which amount increased with SR. The basal texture weakening at high SRs was attributed to extensive tension twinning that occurred in the basal-oriented matrix, which is rarely observed in conventional rolling. Due to the positive effect of texture and microstructure, tensile ductility improvement was significant as compared to that by symmetric rolling. (C) 2011 Elsevier B.V. All rights reserved.