Study on the Indentation Creep Behavior of Mg-4Al-RE-0.8Ca Magnesium Alloy

The indentation creep behavior of Mg-4Al-RE-0.8Ca (AEC4108) alloy was investigated with a homemade apparatus. The microstructure of the AEC4108 alloy and the chemical composition of the precipitation phases in the alloy before and after creep test were investigated by scanning electron microscope and energy-dispersive spectroscopy. The results reveal that the steady-state indentation creep rate of the AEC4108 alloy is increased with increasing temperature and applied stress. The logarithm of the steady-state creep rates is linearly related to the logarithm of the stress and the reciprocal of the absolute temperature. The indentation creep parameters of AEC4108 alloy are correlated using an empirical equation \(\dot{\varepsilon }_{\text{s}} = 1.253\; \times \;10^{ - 8} \times \upsigma^{3.2} \;{ \exp }\left[ { - 33.89/\left( {RT} \right)} \right]\). The thin acicular Al₁₁La₃ and the bone-shaped Al₂Ca are precipitated along the grain boundaries, and the granular Al₂La is formed within the grain. The indentation creep rate of AEC4108 alloy is controlled by the grain boundary slipping led by viscous dislocation movement. The indentation creep resistance of the AEC4108 alloy under temperature 398-448 K and stress 55-95 MPa is guaranteed by the precipitated phases with high thermal stability pinning at the grain boundary and within the grain.