On the path dependence of the thermal vacancy concentration in stoichiometric FeAl

Bulk density and dilatometer measurements were carried out for stoichiometric iron aluminide (FeAl) in order to determine the thermal vacancy concentrations as a function of time and temperature. For temperatures of 600 °C and below the specimen bulk density or length were found to depend on heat treatment history, i.e., they were not unique functions of the temperature. This path dependence suggests a lack of active sources and sinks for thermal vacancies in FeAl at temperatures below ≈600 °C.