Effect of minor Sc on the microstructure and mechanical properties of AZ91 Magnesium Alloy

The as-cast and heat-treated microstructures and mechanical properties of the AZ91 magnesium alloys with and without minor Sc addition were investigated and compared in this paper. The results indicated that adding 0.15-0.45 wt% Sc to the as-cast AZ91 alloy not only could modify and refine the Mg17Al12 phase but also suppress the formation of the Mg17Al12 phase. At the same time, the grains of the Sc-containing as-cast AZ91 alloys were also effectively refined. As a result, the mechanical properties at room temperature (RT) for the Sc-containing as-cast AZ91 alloys were effectively improved. In addition, adding 0.15-0.45 wt%Sc to the AZ91 alloy promoted the formation of the continuous precipitates (CP) during the aging treatment in spite of that the formation of the discontinuous precipitates (DP) was simultaneously suppressed. Accordingly, the Sc-containing as-aged AZ91 alloys obtained the relatively higher mechanical properties at RT than the as-aged AZ91 alloy.