Hydrogen embrittlement of Fe3Al alloys

The tensile and fatigue crack growth behavior of two FeAl alloys, FA-129 and FAP-Y, are described. FA-129 is an ordered intermetallic while FAP-Y is disordered. The intermetallic is embrittled by both laboratory air and by hydrogen gas, while FAP-Y is embrittled only by hydrogen gas. Fractographic features as well as dislocation substructures for both alloys are described. Oxygen is found to provide the highest ductility for FA-129 over a range of test temperatures. The fatigue crack growth rate of FA-129 is influenced by both the type of long-range order and by the test temperature, with the maximum growth rate noted at room temperature. The mechanism of embrittlement by various environments is discussed.