Texture evolution during annealing of AZ31 Mg alloy rolled sheet and its effect on ductility

Abstract

Magnesium sheet alloys have huge potential in automotive closure applications due to their light weight. However, their limited room temperature formability restricts their widespread applications. Microstructure (both geometric and crystallographic) plays a key role in dictating the formability of an alloy. In this research, a systematic study of the microstructure evolution of a hot-rolled AZ31 sheet during thermal annealing was carried out, and the effect of microstructure on room-temperature deformation was characterized. The initial hot-rolled sheet had a dominant basal texture with equiaxed grains and shear bands. The annealing treatment imparted to the sheet alloy triggered an anomalous, inhomogeneous grain growth in grains with a large deviation from the basal orientation. At 350°C annealing temperature, a bimodal grain size distribution of grains with basal and non-basal orientations was observed, and this combination was shown to significantly enhance ductility resulting from a complex interplay between slip and twinning deformation mechanisms. This key finding is expected to contribute to the development of engineered microstructures for enhanced room temperature formability in this alloy.