Effect of mixed rare earth oxides and CaCO3 modification on the microstructure of an in-situ Mg2Si/Al-Si composite

The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope, scanning electron microscope, and energy dispersive spectrum analysis. The results showed that the morphology of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape, their sizes decreased from 75 A mu m to about 25 A mu m, and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth oxides or CaCO3.