DISLOCATION MOBILITY IN (100)-ORIENTED NIAL SINGLE-CRYSTALS CONTAINING IRON AND HAFNIUM ADDITIONS

The dislocation mobility produced by deformation at room temperature h as been studied in [100]-oriented single crystals of NiAl and of those containing hafnium and iron additions. Comparison of the dislocation microstructures produced by compression with those observed after hard ness indentation of thin foils and during in-situ tensile tests in the transmission electron microscope have shown that only [100] dislocati ons are sufficiently mobile in the three alloys. The iron-containing a lloy shows a sufficient density of [111] dislocation segments activate d during compression while the binary and the hafnium-containing alloy s only deform by [100] dislocations because of kinking. The latter gli de preferentially on {110} planes while they are more mobile on {010} planes in the iron-containing material. These differences have been in terpreted as being due to a change in kink density or structure produc ed by the presence of the iron atoms that cause a lower kink mobility on {110} planes in that alloy.