The ambient temperature microhardness of FeAl which contained 28 to 40at%Al was systematically measured after quenching from between 500 and 1000C. The hardness after each annealing temperature went through a minimum at between 30 and 35at%Al. The hardness was independent of annealing temperature at 32at%Al. The thermal vacancy hardening was dependent upon the Al concentration and was reflected by a hardness difference between the 500C annealed state and materials annealed at higher temperatures. The conclusions indicated that vacancy-hardening might not be the only hardening mechanism responsible for the anomalous stress-peak in FeAl alloys.

Thermal Vacancy Hardening in Fe100-xAlx (28<x<40). H.Skoglund, M.K.Wedel, B.Karlsson: Intermetallics, 2007, 15[8], 1127-31