The influence of heat treatment on the microstructure and mechanical properties of the Mg-7Sn-1Si magnesium alloy

Abstract

The influence of precipitation hardening on the microstructure and mechanical properties of the Mg-7Sn-1Si alloy is reported. It was found that the microstructure of the Mg-7Sn-1Si alloy consists of a-Mg solid solution, Mg2Sn and Mg2Si compounds. The solution heat-treatment of the tested alloy at 520 °C for 24 h causes the Mg2Sn phase to dissolve in the a-Mg matrix and spheroidization of the Chinese script Mg2Si compound. Rod-shaped and polygonal precipitates of equilibrium Mg2Sn phase were found in the microstructure after ageing treatment at 200 and 250 °C. The peak hardness is around 58 HV after 120 h at 250 °C and the hardness increment is about 22 HV. The tensile strength of the peak aged alloy is about 120 MPa. The creep rate of the Mg-7Sn-1Si alloy is of order 10−9 at a stress of 30 MPa and temperatures of 200 and 250 °C.