Abstract:Microstructure and texture evolution during high-strain-rate superplastic deformation of the rolled Mg-Gd-Y-Zr sheet were investigated. The tensile tests at the strain rate of 0.01 s⁻¹ achieved the elongations of 180%−266% in the deformation temperature range of 400−500 °C. Post-deforming microstructures were characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy, while crystallographic orientation information was obtained from macro-texture analysis. The results show that the high strain-rate superplasticity was attributed to class-I dislocation creep accommodated by dynamic recrystallization (DRX). During preheating at 435 °C for 600 s, twinning-induced recrystallization occurred. The initial strain of 80% made original grains fragmented and produced homogenous DRX grains. The interaction between dynamic recrystallization and dynamic precipitation yielded out such a phenomenon that finer DRX grains were often accompanied by denser particles. The macro-texture evolution exhibited some characteristics of the crystal rotation arising from basal slip and prismatic slip despite the occurrence of DRX.

Key words: Mg-Gd-Y-Zr alloy; hot rolling; superplastic mechanism; second phases; texture