Constitutive behavior of AZ80 M magnesium alloy compressed at elevated temperature and containing a small fraction of liquid

The constitutive behavior of AZ80 M magnesium alloy was investigated by using compression tests performed at the elevated temperature (400-470 °C) and in the semi-solid state containing a small fraction of liquid with different strain rates (0.001-0.1 s−1), and the microstructure evolution was observed. Considering the influence of liquid phase, a more reasonable constitutive model to describe the peak stress both at the elevated temperature range and in the semi-solid state was obtained. It can be divided into two types: plastic deformation when the alloy is in the solid state (400-470 °C); thixotropic deformation when the alloy is in the semi-solid state (above 520 °C). The average relative errors between the experimental and calculated values are 2.1% and 2.6%, respectively. The activation energy (Q) in the semi-solid state is 289 kJ/mol, which is higher than in the elevated temperature. It is suggested that the presence of liquid phase causes the deformation mechanism in the semi-solid state obviously different from that at elevated temperature.