The dislocation features of a 3at%Hf compound were characterized. Because the general microstructure did not exhibit obvious differences to those observed in similar compounds, the super-dislocation core was investigated in order to find reasons for this effect. Weak-beam conditions were tested which never yielded more than 3 peaks for the intensity profiles. The various fault energies which were related to the core were determined, and were found to be equal to 300mJ/m2 (γ111) and 250mJ/m2 (γ010) at 300K, while γCSF was greater than, or equal to, 460mJ/m2. This was suggested to explain peculiar aspects of the dislocation images. A comparison of the flow-stress versus temperature plots, with those which corresponded to binary and 1at%Ta compounds, confirmed that the shifts which were observed for the flow stress in the anomalous domain (and those for the peak temperature) could be correlated with the γCSF values but not with the antiphase boundary anisotropy ratio. The γCSF value appeared to be the key parameter which controlled dislocation-locking in the strength-anomaly domain. Other solid-solution strengthening effects also operated without impairing the effect of γCSF. This interpretation of differences in the mechanical properties agreed with previous conclusions for similar compounds, and held true when the differences were large. It was also strongly supported by data on dislocation exhaustion rates. The marked ability of super-partials to cross-slip in this large-γCSF Hf compound also explained the relatively large minimum dislocation character for dislocations lying on the octahedral plane.

On the Strengthening of Ni3Al by Hafnium Additions. Kruml, T., Martin, J.L., Bonneville, J.: Philosophical Magazine A, 2000, 80[7], 1545-66