Dislocation structures in small-angle tilt and mixed-character grain boundaries, which formed during the high-temperature annealing treatment of this L12 intermetallic, were characterized by means of transmission electron microscopy. The microscopic observations, under weak-beam imaging conditions, showed conclusively that the super-dislocations which comprised the boundaries were narrowly dissociated on the {001} and {111} planes, with {001} and {113} being the respective contact planes for the tilt and mixed-character boundaries. The antiphase boundary energies were calculated by using the Marcinkowski force balance equation which was based upon isotropic elasticity and by balancing the forces for an isolated dissociated super-dislocation by using both isotropic and anisotropic elasticity. The values of antiphase boundary energies which were obtained by using these 3 methods were essentially the same for both the {001} and {111} planes; provided that the image shifts which occurred during weak-beam imaging were accounted for. When compared with observations on Ni3Al, the similarity of these measurements suggested that anisotropic elasticity played a lesser role in determining the dissociation distance in Ni3Ge. The values were also in good agreement with those previously obtained after room temperature deformation. This suggested that there was no appreciable dependence of the cube-plane antiphase boundary energy upon temperature in the present material.

Characterization of Dislocation Structures Associated with Small-Angle Boundaries in Annealed L12 Ni3Ge M.Kumar, K.J.Hemker: Philosophical Magazine Letters, 1997, 76[6], 399-407