Characterization of Al–Si–Mg alloys fast quenched from the melt by special medium

A novel fast cooling technology, melt-liquid-quenching (MLQ) with special cooling medium, was invented to prepare Al–7.0 wt.%Si–0.4 wt.%Mg alloys. The microstructure and mechanical properties of the alloy was investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), microhardness (HV) and tensile strength testing method. The DSC results showed that exothermal peak around 260 °C of Al–7%Si–0.4%Mg alloys obtained by MLQ method is broader than that obtained by water-cooling copper mould (WCCM). When the specimens obtained by these two methods were aged at 260 °C for 8 h, no exothermal peaks were found. This demonstrated that, cooling rate of melt obtained by MLQ method is faster than that obtained by WCCM method. Microstructure of the castings obtained by MLQ was refined obviously and both microhardness and ultimate tensile strength (UTS) of the alloy were 33.3 and 22.9% higher than those made by WCCM, respectively.