Effect of hot rolling on grain refining and mechanical properties of AZ40 magnesium alloy

AZ40 Mg alloy thin sheets were prepared by multi-pass hot rolling with the hot-extruded alloy as the starting material. The effect of hot rolling on the microstructure, mechanical properties, and fracture behavior of the alloy was investigated. The results show that the microstructure homogeneity can be improved and the grain size is refined steadily by dynamic recrystallization with increasing rolling passes. As a consequence, the mechanical properties of the as-rolled sheets are improved significantly as compared with the starting as-extruded alloy. By 5 or more rolling passes, the average grain size is reduced to no more than 10 μm, and the yield strength and the tensile elongation of the sheets prepared achieve as high as more than 175 MPa and 20%, respectively, in both the rolling and the transverse direction.