Superplastic behaviors of a Mg-Zn-Y-Zr alloy processed by extrusion and equal channel angular extrusion

摘要

Superplastic deformation (SPD) behaviors of a Mg-5.8 percent Zn-1.0 percent Y-0.48 percent Zr alloys produced by conventional extrusion and equal channel angular extrusion (ECAE) methods, respectively, have been comparatively studied in this paper. It is found that the optimum superplastic condition in as-extruded alloy was obtained at 450 deg C and 3.3 X 10~(-4) s~(-1) with the largest elongation to failure about 450 percent; while in as-ECAEed alloy it was at 350 deg C and 1.7 X 10~(-3) s~(-1) with about 800 percent elongation. Microstructural observations showed that structure evolution and cavity formation behaviors were different in these two materials during SPD. The probable mechanisms for superplasticity such as grain boundary sliding (GBS) and dynamic recrystallization (DRX) under different deformation conditions were discussed in terms of strain rate sensitivity, activation energy, as well as microstructural evolution.