Hot hardness and creep of Fe3Al-based alloys

Hot hardness and creep studies were carried out on Fe3Al and Fe3Al containi ng Cr or Ti. Indentation and impression creep testing methods were employed to characterize the creep behaviour. Compared to the binary alloy, Fe3Al-C r exhibits a lower hardness indicating solid-solution softening effect of C r. On the other hand, solid-solution hardening effect of Ti is significant in the temperature range 300-900 K. Results from indentation creep indicate s that a power-law creep behaviour (n between 6 and 8) is observed in the b inary and Cr containing alloys at temperatures greater than 753 K. At lower temperatures in the above two alloys and in the Ti-containing alloy even a t higher temperatures, there is a power-law break down. On the other hand a t low stress levels covered in the impression creep studies, power-law cree p is observed in all the alloys in the stress and temperature range of inve stigation. Under these conditions, all the alloys exhibit a stress exponent value of around 3 for the steady state creep rate. The activation energy f or creep is estimated to be in the range 325 and 375 kJ mel. Among the allo ys studied, Fe3Al-Ti exhibits the best creep resistance. The results indica te that in the B2 region, viscous glide controls the creep rate at low stre sses while climb of dislocations may be rate controlling at higher stresses . (C) 2000 Elsevier Science Ltd. All rights reserved.