Dependence of the yield stress of Fe3Al on heat treatment

The room-temperature yield strength of quenched FeAl-based iron aluminides depends strongly on the temperature from which the quench occurs. There is evidence that Fe3Al-based iron aluminides show similar behavior, albeit not as pronounced. The purpose of this work was to carry out quenching and annealing experiments to clearly demonstrate this effect, as well as to study its kinetics. Room-temperature compression tests were performed using cast Fe-28at%Al and Fe-30at%Al after quenching from temperatures in the range 300–1000 °C. Kinetic studies were carried out to assess the reduction of the yield stress by subsequent annealing for various times at relatively low temperatures. Results from the present study are compared with data available in the literature and explanations for the dependence of room-temperature mechanical behavior on annealing history are evaluated. It is concluded that room-temperature strengthening in Fe3Al-based iron aluminides is consistent with behavior expected for quenched-in thermal vacancies and this could be an important strengthening mechanism in Fe3Al.

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► Fe3Al was investigated on room-temperature mechanical properties by annealing at different temperatures.
► The observed strengthening was found to be consistent with vacancy hardening.
► The reduction of room-temperature yield stress is consistent with published time constants for vacancy migration and removal.
► Vacancy migration and removal are such that thermal vacancies can be frozen in by quenching from temperatures as high as 900 °C.
► It is concluded that the yield strengths are consistent with thermal vacancy controlled room-temperature strengthening.