Yield stress and dislocation mechanisms in the D03 ordered intermetallic phase Fe3Al in the temperature range 240–500 K

In pure D03 ordered Fe3Al single crystals with low carbon content the yield stress shows a pronounced drop in a narrow temperature range around 375 K, connected with the movement of single partial dislocations with extended antiphase boundaries at lower, and of complete superdislocations at higher temperatures. This is supported by measurements of the temperature and strain rate dependence of the critical resolved shear stress in the lower temperature regime and their quantitative analysis according to Seeger’s kink-pair nucleation theory. The rapid transition between these two regimes is explained by positive feedback mechanisms which stabilize the different situations, based on the relative frequencies of kink-pair nucleation and motion.