The interfacial structure of body-centered cubic laths which precipitated from a Ni-rich face-centered cubic matrix was studied by using transmission electron microscopy. Some 50 precipitates, and more than 200 defects in their vicinity, were analyzed. High-resolution electron microscopic images revealed that the parallel conjugate planes of the Kurdjumov-Sachs orientation relationship were continuous across the broad faces of the laths. The (1¯21)f habit plane contained structural ledges and irregularly spaced dislocations, but no regular array of misfit dislocations. Some 87% of the dislocations in the habit plane had Burgers vectors in the conjugate plane. These dislocations were found in the risers of growth ledges, and had to climb as the ledges migrated. The dislocations accommodated misfit in the conjugate planes of the orientation relationship, while misfit perpendicular to these planes was compensated by elastic strain. Stacking faults were found to extend into the matrix from the precipitate habit plane. These accommodated elastic strain, and appeared to aid the formation of growth ledges. On the side facet of the precipitate lath, 2 types of linear defect were found. These were misfit dislocations that were spaced 12nm apart, with 1/3[1¯11]f Burgers vectors, and structural ledges parallel to the misfit dislocations which were spaced 1.5nm apart. The misfit dislocations were in a sessile orientation with respect to growth of the side facet.

Interfacial Structure and Growth Mechanisms of Lath-Shaped Precipitates in Ni-45wt%Cr J.K.Chen, G.Chen, W.T.Reynolds: Philosophical Magazine A, 1998, 78[2], 405-22