Observation of quenched-in vacancies in the B2 intermetallic compounds, FeAl

The concentrations of quenched-in vacancies retained in B2 Fe1-cAlc alloys were obtained as functions of composition (0.39 < c < 0.51) and quenching temperature (773 to 1273K) from lattice constant and density measurements. Obtained vacancy concentration indicated a gradual increase with composition in the lower Al content region, while it increased rapidly when approaching stoichiometry. Slow-cooled (1K/min) samples showed that retained vacancy concentration is higher than that for samples annealed at and quenched from 773K. Relations of vacancy concentration to the lattice constant, quenching temperature and hardness were discussed. Present results well supported the hardening effect due to retained vacancy and further the proposed linear relation of hardness to the square root of vacancy concentration.