The dislocation structures present in a directionally solidified Ni3Al-base alloy after tensile testing in the [001] orientation at 850C were studied using transmission electron microscopy weak beam techniques. Most dislocations were of the antiphase boundary pair type. Superlattice intrinsic stacking faults were also observed, but they were rare. The ½<110> dislocation pairs were present mostly with screw character. They were confirmed to be the Kear-Wilsdorf configurations. Non-screw segments of the ½<110> dislocation pairs were dissociated on {111} planes. Movement of the ½<110> dislocation pairs in {010} planes was found to be the result of a thermal activation and interactions between the screw segments and the non-screw segments. It was suggested that deformation was mainly the result of the non-screw segments slipping in the {111} planes. As the ½<110> dislocation pairs become screw oriented, they cross-slip onto the {010} planes and may sometimes bend in these planes. Thus, further movement of the non-screw segments in the {111} planes requires drawing back the screw segments from the {010} to the {111} planes.

A Transmission Electron Microscopy Study of Dislocation Structures in a Directionally Solidified Ni3Al-Based Alloy Deformed at 850C. Wen, M., Lin, D.: Materials Science and Engineering A, 1992, 152[1-2], 208-11