INTERFACIAL STRUCTURE OF GRAIN-BOUNDARY PRECIPITATE IN A NI-45 MASS PERCENT CR ALLOY

Interfacial structure of b.c.c. precipitates formed at f.c.c. matrix grain boundaries in a Ni-45 mass%Cr alloy was examined by means of transmission electron microscopy (TEM). The grain boundary precipitates had nearly the Kurdjumov-Sachs orientation relationship with respect to one of the matrix grains forming the grain boundary though the orientation relationship with respect to the other grain is, in general, irrational. Irregularly aligned growth ledges were observed as well as a parallel array of straight misfit compensating dislocations (or ledges) with a uniform spacing, not only on the K-S related interface but also on the irrationally related interface. This result suggests that the interfaces of the grain boundary precipitates are partially coherent on both matrix grains.