Defect and atomic ordering studies in highly deformed and disordered Fe72Al28 alloy

The results of positron annihilation and Moessbauer spectroscopies in Fe72Al28 alloy with different structural morphology obtained by severe deformation and by quenching from a high temperature are presented. The changes in atomic ordering and in defect arrangements after recovery and ordering annealing in both highly deformed and highly disordered samples are also pursued and discussed. It is shown that the dominant component of 184 ps in the positron lifetime spectrum of a highly disordered sample corresponds to the annihilation in vacancies which prefer to occupy that sublattice in D03 superstructure containing both aluminum and iron atoms. Important changes in vacancy concentration take place only when an annealing above D03↔B2 (823 K) is performed. Temperature treatment below this phase transformation temperature is characterized above all by changes in the density of dislocations.