Effect of environment on tensile ductility and fracture toughness of iron aluminides

The effects of environment on the tensile ductility and fracture toughness of Fe-28at.%Al and Fe-35at.%Al are investigated. Room-temperature fracture toughness of the iron aluminides investigated in air ranged between 35 and 40 MPa m1/2, significantly higher than those of many ordered intermetallic alloys. A significant effect of environment is observed on the tensile ductility and fracture toughness. The effect of environment is more significant in Fe-35Al compared with Fe-28Al. The fracture surface morphology of the specimens tested differed in test environments in B2 ordered Fe-28Al and Fe-35Al, while in D03 ordered Fe-28Al it was more or less similar, mostly transgranular cleavage, in all the environments tested. Increased intergranular fracture regions were observed in B2 ordered Fe-28Al and Fe-35Al when tested in vacuum and oxygen, compared with that tested in air.