Preparation and characterization of as-rolled AZ31 magnesium alloy sheets

The AZ31 magnesium alloy sheets were hot-rolled by using a small sized rolling mill. The thickness was successfully reduced to 0.6 mm without surface cracks. The effects of rolling reduction on microstructure and hardness of the thin sheets were investigated. The rolled sheets of less than 1 mm in thickness had a preferred orientation (image) and a very fine-grained homogeneous microstructure with an average grain size of about 20 μm as a result of dynamic recrystallization. The eutectic precipitates (α-Mg and β-Mg17Al12) changed gradually from a blocky structure to small particles of about 5 μm with increasing reduction, through the diffusion of the eutectic precipitates from the grain boundaries to the inner of the refined grains during the hot rolling. The hardness of the as-rolled samples increased initially from 50 to 80 HV with increasing reduction, and reached the highest value of 90 HV at 97% reduction in thickness.