Effect of heat treatment on gravity die-cast Sc-A356 aluminium alloy

The effects of scandium addition (0.00 wt.%, 0.2 wt.%, 0.4 wt.% and 0.6 wt.%) and T6 heat treatment on the microstructure and mechanical properties of A356 aluminium alloy have been investigated in the research reported in this paper. The Sc inoculated specimens were prepared by gravity die-casting, according to ASTM B557-06 standard. The cast samples were then subjected to heat treatment at solutionizing temperature of 540 degrees C for 8 h followed by water quenching and artificial aging at 160 degrees C for 6 h. The microstructure, microhardness and tensile strength of the heat-treated samples were examined with use of scanning electron microscope (SEM), optical microscope, Vicker's hardness tester, and Instron static machine respectively. Heat treatment was found to be able to effectively reduce grain size down to 16 mu m (0.6 wt.% Sc), from 40 mu m (original A356). The tensile strength was significantly improved, up to 338 MPa for heat treated 0.6 wt.% Sc-A356 having been achieved. The microhardness of 118 HV has been obtained for heat treated 0.6 wt.% Sc-A356.