A re-examination of the pinning mechanisms responsible for the stress anomaly in FeAl intermetallics

Fe–Al alloys, both those based on Fe3Al and those based on FeAl, show an anomalous increase in flow stress for temperatures in the range about 500–900 K. Some of the important characteristics of the experimental results collected over decades of study are reviewed, concentrating here on FeAl alloys with B2 order. Particular attention is given to the influence of vacancy concentration and the stress orientation when testing single crystal samples. Recent analyses deduce that the stress anomaly is caused by the high concentration of vacancies present at these temperatures. Re-analysis here of the hardening suggests that vacancies may annihilate at the dislocation cores and the new jogs may be suitable sites for subsequent dislocation decomposition into less mobile segments.