Magnetic and calorimetric study of point defects in FeAl intermetallic compound

The behaviour of point defects has been investigated in quenched B2-FeAl intermetallic compounds by using magnetic susceptibility measurements χ(T) and differential scanning calorimetry (DSC). During an isochronal annealing, the observed step in magnetic susceptibility at about 410°C reflects the migration of iron antistructure atoms, frozen by the quenching process, to their own sites. Several thermal phenomena have been detected by means of DSC measurements. The principal peak, attributed to the migration and elimination of iron antistructure atoms via vacancy mechanism, depends on the quenching temperature Tq: for Tq=1000°C, the annealing-out temperature range is lower by about 150°C than for Tq=800°C. The concentration of eliminated vacancies, during this stage, has been determined from fitting the experimental χ(T) curves by the Curie–Weiss law: it was found to be 1.76×10−2 for the equiatomic composition and 1.73×10−2 for the Fe49Al51 compound. The annealing kinetics study allows us to determine the migration enthalpy of 1.95 eV taking into account the formation of vacancy clusters.