INVESTIGATIONS OF DISLOCATION MECHANISMS IN NI3AL AT DIFFERENT TEMPERATURES - IN-SITU STRAINING EXPERIMENTS IN A TRANSMISSION ELECTRON-MICROSCOPE

The glide of dislocations in the octahedral planes of Ni3Al is studied in situ between 165 and 1 123 K. Different microscopic behaviours are observed in the low- and high-temperature ranges of the yield stress anomaly domain, and at temperatures above the peak. Local stress measu rements and respective intensities of glide in cube and octahedral pla nes are consistent with results of other techniques. Experimental resu lts in the temperature range of yield stress anomaly are interpreted i n terms of double-cross-slip processes between octahedral and cube pla nes, and octahedral glide at temperatures above the peak in stress inv olves diffusion processes.