Effects of minor additions of cerium, silicon and calcium on microstructure and mechanical properties of AZ91 magnesium alloy

Abstract The effects of minor Ce, Si and Ca additions on the microstructure and mechanical properties of the as-cast and T6 state AZ91 alloy were analyzed and compared in this paper by means of optical microscopy, scanning electronic microscopy, X-ray diffraction and tensile testing. Results showed that the addition of Ce and Ca could effectively modify the β-phase and the average grain size was refined from 239.7 ± 16.9 μm in AZ91 alloy to 57.8 ± 1.4 μm in AZ91-1.0Ce-0.5Ca alloy. Accordingly, the as-cast AZ91-1.0Ce-0.5Ca alloy showed optimum yield strength of 119 MPa and elongation of 10.7 %. Furthermore, AZ91-1.0Ce-0.5Ca alloy possesses a higher effect in the reduction of the discontinuous precipitates after aging and the yield strength increased to 164 MPa with elongation of 11.8 %.