The recovery of Quenched‐in Vacancies in Fe–Al (6.3 to 28.3 at.%) Alloys studied by Positron Annihilation

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Abstract
Measurements of the peak height of the 2γ‐angular correlation curve were carried out during constant rate heating of Fe–Al alloys with an Al‐content between 6.3 and 28.3 at.%. The samples had been quenched form 1000°C into water at room temperature. Two recovery stages are observed. The first stage at 100 to 200°C shows a small decrease of the peak height. The main stage at 300 to 400°C is attributed to the migration and disappearance of monovacancies. From isothermal measurements the migration enthalpy of vacancies is estimated to (1.15 ± 0.1) eV in Fe–Al (19.9 at.%) and to (1.31 ± 0.1) eV in Fe–Al (24.4 at.%). – In samples with an Al‐content between 13.8 and 28.3 at.% a minimum in the peak height at 400°C is found. Obviously a particular stage is formed in these samples during migration of quenched‐in vacancies. Possible causes of the effect are discussed.