The effect of trace Sc on the quench sensitivity of AL–7Si–0.6 Mg alloys

Abstract

The Jominy end quench test has been adopted to investigate the effect of trace scandium on the quench sensitivity of Al–7Si–0.6 Mg alloys. The results show that at a lower quenching rate, the preferred precipitation of the Al3Sc phase inhibits the formation of a β′-Mg2Si phase, promoting the nucleation of finely dispersed metastable Mg2Si precipitates in the subsequent aging treatment. The quench sensitivity of the Al–7Si–0.6 Mg alloy was effectively improved by more than 60%.Rapid quenching rates can cause the Al matrix of the alloy to be in a supersaturated state, resulting in enhanced mechanical properties after aging treatment. In contrast, slow quenching rates precipitate the relatively coarse β′-Mg2Si phase and also produce a precipitate free zone during the quenching process, thereby diminishing the mechanical properties of the alloy after the aging treatment, so that the Al–7Si–0.6 Mg alloy possesses higher quench sensitivity.