Abstract: The mechanical behavior of Fe3Si based alloy with B2 structure was studied by tension and fracture toughness test in various tsting media.The fracture strength σb of Fe3Si alloy decreased in the following order:oxygen,air and hydrogen respectively.The fracture toughness in different testing environment showed that KIC in oxygen is 11.5±0.3MPα·m^1/2,and is 8.6±0.4MP α·m^1/2 in distilled water.The reduction of fracture toughness is contributed to the environmental reaction of Si with water.Addition of Al element in Fe3Si is not beneficiol to improve the intrinsic ductility of Fe-14Si-3Al alloy.The scattering phenomenon of fracture strength was found,and explained by fracture mechanics.It was found by means of SEM that the fracture mode changed from transgranular in oxygen to intergranular in hydrogen gas and distilled water.

Key words: Fe3Si, intermetallic, mechanical behavior,