Influence of initial microstructure on the hot working flow stress of Mg–3Al–1Zn

The hot working flow stress is examined for wrought and as-cast magnesium alloy AZ31, deformed in both compression and torsion. It is found that the hot deformation behaviour is sensitive to the deformation conditions, initial microstructure and the deformation mode. The peak stresses in compression are higher for as-cast material at low strain rates and high temperatures, whereas they are higher for fine-grained wrought material at high strain rates and low temperatures. Also, the stress–strain curves in torsion exhibit considerably higher strains to the peak flow stress than in compression, particularly at lower temperatures. Most noticeably in the compression of the wrought material, the shape of the stress–strain curves change considerably as the temperature is reduced and the strain rate is increased. These key features of the deformation behaviour are explained in terms of initial grain size, texture, twinning and dynamic recrystallization.