Microstructure evolution of semi-solid Mg2Si/A356 composites during remelting process

The semi-solid processed Mg2Si/A356 composites were fabricated using a sloping plate, and the phase and morphology evolution of the semi-solid Mg2Si/A356 slurry during the remelting process was investigated. Results indicate that compared to as-cast microstructure, the size of primary α-Al phase and Mg2Si phase of semi-solid microstructure fabricated by using a sloping plate decreases and the morphology of α-Al phase becomes fine and globular. With increasing the reheating temperature and prolonging the holding time, the primary α-Al phase spheroidizes, the liquid fraction in semi-solid microstructure increases, and the Chinese script Mg2Si phase embedded in the primary α-Al phase cannot be observed. The Chinese script Mg2Si phase is distributed in the secondary α-Al phase and becomes smaller. The net-shaped eutectic phase also becomes finer after reheating. The optimum remelting parameters suitable for thixoforming in this study are remelting at 580 °C for 30 min.