The processes of thermomechanical treatment adopted on AZ31 magnesium alloy are solution treatment,pre-ageing,deformation and ageing.This paper focuses on the effects of the preageing and the subsequent deformation on its microstructure and mechanical properties.The experimental results show that most second phase of Mg_(17)Al_(12) dissolved into the substrate ofα-Mg and thermomechanical treatment is one of effective process to improve the property of AZ31 alloy.The effect of pre-ageing before deformation i...