Decorrelated movements of Shockley partial dislocations in the γ-phase channels of nickel-based superalloys at intermediate temperature

Abstract

In nickel-based superalloys with high volume fraction of γ′ precipitates, dislocations have to experience high curvatures in order to enter narrow channels by glide in the {111} planes of the fcc γ matrix. Observations of in situ dynamic sequences performed in a transmission electron microscope on several industrial superalloys have shown the occurrence of decorrelated movements of Shockley partial dislocations, originating from perfect dislocation dissociation. By evaluating the effective stress acting on each one of these partial dislocations, as well as their respective flexibility, the possible occurrence of such movements for some particular dislocation characters and channel widths is accounted for. These movements can play an important role in the creep behaviour of these materials in the low deformation rate regime.

Acknowledgments

The authors thank Professor J.L. Strudel for allowing their ideas to mature before writing and for his clear help in improving the manuscript. They are indebted to P. Veyssière for the concept of “channels filtering” the dislocations. They want to express their gratefulness to J. Crestou for his talent in the preparation of samples. A part of this study was financially supported by the RRIT “Recherche Aéronautique sur le Supersonique”, Ministère de la Recherche et des Transports.