Effects of cooling rate on solution heat treatment of as-cast A356 alloy

The effect of cooling rate of the solidification process on the following solution heat treatment of A356 alloy was investigated, where the cooling rates of 96 K/s and 3 K/s were obtained by the step-like metal mold. Then the eutectic silicon morphology evolution and tensile properties of the alloy samples were observed and analyzed after solution heat treatment at 540 °C for different time. The results show that the high cooling rate of the solidification process can not only reduce the solid solution heat treatment time to rapidly modify the eutectic silicon morphology, but also improve the alloy tensile properties. Specially, it is found that the disintegration, the spheroidization and coarsening of eutectic silicon of A356 alloy are completed during solution heat treatment through two stages, i.e., at first, the disintegration and spheroidization of the eutectic silicon mainly takes place, then the eutectic silicon will coarsen.