Investigation of semi-solid microstructures of an A356 alloy containing rare-earth Gd during isothermal heat treatment

The effects of isothermal heat treatment on microstructures of an A356 alloy containing rare-earth gadolinium (Gd) were investigated to obtain an optimum semi-solid structure. Our results revealed that the primary alpha-Al phase of the semi-solid A356 alloy containing Gd was significantly refined and that its morphology was spherical or near-spherical. Increases in holding temperature and prolongation of holding time led to an initial decrease in size during the primary alpha-Al phase, followed by a gradual increase. Solid-liquid interfacial tension resulted in the spheroidization of the primary alpha-Al phase.