Mechanical properties of cast A356 alloy, solidified at cooling rates enhanced by phase transition of a cooling medium

Phase transition cooling (PTC), using the absorbed latent heat during the melting of phase transition cooling medium to cool and solidify alloys in the process of casting, is a new fast cooling technology. Specimens of A356 casting aluminum alloy were prepared by this method. For comparison, specimens made by water-cooling copper mould (WCCM) were prepared too. The mechanical properties of A356 alloy made by PTC and WCCM were measured by microhardness and tensile strength testing methods. Microstructures of A356 alloy were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-rays diffraction (XRD). The results show that both microhardness and ultimate tensile strength (UTS) of A356 alloy made by PTC method are much higher than those made by WCCM method. This can be attributed to the refined microstructure and the extended solubility of silicon in α-Al. The solubility of silicon in α-Al was 2.7 at.% in specimens solidified in phase transition cooling medium and 2.4 at.% in specimens solidified in water-cooling copper mould.