Improvement in impression creep property of as-cast AC515 Mg alloy by Mn addition

The effect of Mn on the impression creep behavior and microstructure of AC515 (Mg–5Al–1.5Ca) alloy has been studied. Four alloys based on AC515 with different Mn contents 0, 0.3, 0.5 and 0.8 wt% were prepared. The study showed that the impression creep properties of AC515 alloy are significantly improved by Mn addition. Addition of Mn up to 0.5 wt% increases the impression creep resistance, whereas incorporation of 0.8 wt% Mn decreases the impression creep resistance of samples. The microstructure of AC515 alloy consists of (Mg,Al)2Ca distributing in the α-Mg matrix. Addition of Mn causes formation of Al8Mn5 in matrix and interdendritic regions. The stress exponent and activation energy are in the ranges of 5–6 and 97.3–99 kJ/mol, respectively, for all alloys. The suggested creep mechanism under the experimental conditions is pipe diffusion dislocation climb.