Interfacial dislocation networks around γ′ precipitates in nickel-base alloys

The three-dimensional dislocation network covering the γ–γ′ interface in a nickel-base superalloy was observed and identified by transmission electron microscopy. Estimates of the lattice misfit yielded about – 0·3% in the alloy considered. Assuming all dislocations to be of pure edge character the complete network could be analysed as formed by a/2〈110〉 dislocation loops extending over a tetrakaïUdecahedron: the eight {111} faces are covered with hexagonal dislocation networks, while the six {001} faces exhibit square and octagonal dislocation arrangements resulting from the interaction of dislocations with orthogonal Burgers vectors. The importance of interfacial dislocation networks and the role of the lattice misfit in oriented γ′ coalescence during creep are pointed out.