Effects of hot rolling processing on microstructures and mechanical properties of Mg-3%Al-1%Zn alloy sheet

The microstructure evolution and deformation mechanisms of AZ31 alloy sheet during hot rolling were investigated. The initial microstructure in the as-received AZ31 sheet shows basal texture with an average grain size of 37 mu m. During the subsequent hot rolling processing, dislocation slip occurs in addition to extension, contraction and double twinning, and the twinning mode is dependent on the grain orientation, grain size and rolling temperature. Continuous dynamic recovery and recrystallization (CDRR) is the main mechanism of grain refinement for the AZ31 sheet during hot rolling, and the {-1 0 1 1} contraction and {-1 0 1 1} - (1 0 - 1 2) double twinning accelerate the refinement process. Contraction and double twinning have positive effect on grain refinement and texture randomization for the AZ31 alloy during hot rolling. In this study, higher per-pass reduction of 50% and higher rolling temperature of 400 degrees C led to more uniform grain structure with more random texture, which resulted in the higher ductility than that of the sheet samples rolled at 300 degrees C and at per-pass reduction of 30%. Therefore, higher temperatures and larger per-pass reduction rolling are recommended for microstructure optimization and the mechanical properties improvement of the AZ31 sheet. (C) 2009 Elsevier B.V. All rights reserved.