Thermal vacancy hardening in Fe100−xAlx (28 < x < 40)

The ambient temperature microhardness of FeAl containing 28–40 at.% Al has been systematically measured after quenching from a range of annealing temperatures between 500 and 1000 °C. The hardness for each annealing temperature has a minimum located between 30 and 35 at.% Al, and the hardness is independent of annealing temperature at 32 at.% Al. The thermal vacancy hardening is dependent on Al concentration and is documented by the hardness difference between the 500 °C annealed state and materials annealed at higher temperatures. Furthermore, our conclusions indicate that vacancy hardening might not be the single hardening mechanism responsible for the anomalous stress peak in all FeAl alloys.