ROOM-TEMPERATURE FRACTURE OF FEAL AND NIAL

The room temperature fracture behavior of the B2 compounds FeAl and NiAl has been examined as a function of alloy stoichiometry. In tension tests, iron-rich FeAl (less-than-or-equal-to 45 at.% Al) exhibited some ductility whereas the stoichiometric compound is brittle. In contrast, stoichiometric NiAl shows ductility but nickel-rich compositions are brittle. For both FeAl and NiAl fracture is predominantly intergranular at the stoichiometric compositions and becomes increasingly transgranular with decreasing aluminum concentration. For FeAl good quality selected area channeling patterns (SACP) could be obtained from the intergranular facets of the stoichiometric compound but not from iron-rich alloys. In contrast, good quality SACPs could be obtained from all the NiAl alloys.