Mechanical properties of FeSi, FeSi2 and Mg2Si

FeSi, a-FeSi2 (high-temperature modification) and Mg2Si are the major phases in ferro-silicon-magnesium (FeSiMg) based foundry alloys used for production of ductile cast iron. Small quantities of these phases were produced by induction melting for a more detailed study of the behaviour of each phase. The chemical composition of each phase was verified by electron microprobe analyses (EPMA). Investigation of the microstructure showed the existence of a small amount second phases in the produced samples. Compression tests were performed to determine the elastic modulus of each compound. The fracture toughness of FeSi was established from three-point bending tests and was compared with values calculated from Vickers indentations. For a-FeSi2 and Mg2Si, the fracture toughness was estimated from hardness indentation tests. Palmqvist type of cracks developed from the corners of the indentations marks in all three phases.