The weak-beam technique of transmission electron microscopy was used to analyze a new shearing configuration of γ′ precipitates after the creep, at 700C, of a Ni-based superalloy. The shearing configurations were made up of superlattice extrinsic stacking faults, matrix stacking faults and individual (a/6)<112> Shockley dislocations. This mechanism was initiated by the uncorrelated movement of the 2 Shockley partials of a single (a/2)<110> matrix dislocation. The propagation of the leading partial created this shearing process. This behavior, that occurred in small γ channels due to the flexibility of dislocations, could be used to evaluate microstructural evolution during aging.

On the Shearing Mechanism of γ′ Precipitates by a Single (a/6)<112> Shockley Partial in Ni-Based Superalloys. B.Décamps, S.Raujol, A.Coujou, F.Pettinari-Sturmel, N.Clément, D.Locq, P.Caron: Philosophical Magazine, 2003, 84[1], 91-107