Microstructure, mechanical properties and deformation mechanism of powder metallurgy AZ31 magnesium alloy during rolling

Abstract

To improve the microstructure compactness and mechanical properties of powder metallurgy (P/M) AZ31 magnesium alloy, hot rolling deformation was carried out in this work. The effect of rolling reduction on the microstructure and mechanical properties of P/M AZ31 magnesium alloy was investigated systematically. The results show that the equiaxed-shape prior particles gradually elongated along the rolling direction and evolved into banded-shape with the increase of rolling reduction. The grains with random orientation distribution gradually evolved into preferred orientation distribution, and the grain size gradually decreased. When the rolling reduction increases from 0 to 80%, the relative density, ultimate tensile strength and Vickers hardness increase from 98.03%, 244.37 MPa and 55.95HV to 98.5%, 296.56 MPa and 66.89HV, respectively, while the elongation decreases from 22.97% to 12.22%. A strong basal texture with (0001) basal plane parallel to the rolling surface was mainly formed in the alloy after hot-rolling. The improvement of mechanical properties of the alloy after hot-rolling was mainly due to the increase of microstructure compactness and fine grain strengthening. When the rolling reduction was small, the deformation was mainly dominated by slip and twinning; while when the rolling reduction was large, the deformation was mainly dominated by slip and dynamic recrystallization.