Microstructure and Impression Creep Properties of Ca-Containing AS31 Magnesium Alloy

The effect of Ca addition on the microstructure and impression creep properties of AS31 magnesium alloy was investigated in the current study. The results showed that the microstructure of AS31 alloy is composed of α(Mg) phase, massive Mg17Al12 and some Chinese script Mg2Si compounds. Addition of 2 wt% Ca to AS31 alloy resulted in complete elimination of Mg17Al12 phase and formation of Al2Ca compound. Ca improved the alloy’s creep properties especially at higher temperature. Improvement in the creep properties was attributed to the elimination of soft Mg17Al12 and formation of thermally stable Al2Ca compound. According to the obtained stress exponent and creep activation energy, pipe diffusion climb-controlled creep was estimated as the dominant creep mechanism and Ca had no influence on the dominant mechanism.