Creep behavior of high-pressure die-cast Mg-4Al-4La-0.4Mn alloy under medium stresses and at intermediate temperatures

Tensile creep behavior of the high-pressure die-cast Mg-4Al-4La-0.4Mn alloy under stresses of 50-100 MPa and at 150-225 °C was thoroughly investigated. This alloy exhibits a stress exponent of approximately 6 and the activation energy Q falls within the range of 80-120 kJ/mol at 150-200 °C. From fitting results, the commonly adopted threshold stress approach is not suitable for ALa44 alloy, and the normalized stress exponent is approximately 7, suggesting that creep deformation of ALa44 alloy was controlled by low-temperature dislocation climb (core diffusion). Furthermore, the microstructural analysis results indicate that the rate-controlling creep mechanism of ALa44 alloy is dislocation climb, but the cell boundary disintegration and the dislocation cross-slip also assisted deformation during creep processes.