Effect of tin on the microstructure and impression creep behavior of MRI153 magnesium alloy

The effect of tin on the microstructure and creep behavior of as cast magnesium MRI153 alloy was investigated in the present study. Creep behavior of the alloys were studied using impression creep test under shear modulus normalized stress ranging from 0.025 to 0.04 at temperatures of 152-217 °C. Results showed that adding tin to MRI153 alloy reduces the amount of Al2Ca via forming CaMgSn phase, whereas the continuity and value of Mg17Al12 phase are increased. Solubility of calcium in Mg17Al12 phase is also reduced in the presence of tin. It was shown that adding tin to MRI153 alloy decreases the alloy creep strength, which can be attributed to the reduced value of Al2Ca phase and formation of CaMgSn phase instead as well as reduced thermal stability of Mg17Al12 phase and its increased value and continuity. By calculating creep activation energy and stress exponent, it was shown that although climb-controlled dislocation creep is the dominant mechanism in the creep of these alloys, the creep activation energy is decreased with increasing the amount of tin.