In-situ microscale examination of hydrogen effect on fracture toughness: A case study on B2 and D03 ordered iron aluminides intermetallic alloys

The hydrogen embrittlement phenomenon of iron aluminides (Fe3Al and FeAl) at microscale was investigated by microcantilevers bending tests with a (1 0 0)[0 0 1] crack system. The cantilevers were loaded in-situ in an environmental scanning electron microscope under two conditions: one with water vapor to promote hydrogen uptake and the other one with high vacuum as a reference state. Fe3Al shows a distinguished cleavage fracture behavior when tested under both conditions. The microscale fracture toughness of Fe3Al was evaluated by linear elastic fracture mechanics and the basic J-integral method. FeAl, however, exhibited a stable cracking behavior and thus the fracture toughness was characterized using iterative J-integral method. For both materials, the hydrogen is found to reduce the maximum bearing load and enhance the cracking process.