On the temperature dependence of the yield stress in Fe3Al single crystals in the range of 300 to 500 K

The temperature dependence of the critical resolved shear stress of Fe3Al single crystals exhibits not only the well-known high temperature anomaly with rising stress but also a sharp decrease of the yield stress in a narrow temperature range somewhat above ambient temperature. This drop is connected with a characteristic change of the operative deformation mechanism, resulting in a specific behaviour of slip line evolution on the sample surface, which is monitored by means of an optical microscope during deformation. In addition to the yield stress, the strain rate sensitivity and the work hardening rate show characteristic changes in this particular temperature range.