Atomic study on the interaction between superlattice screw dislocation and gamma-Ni precipitate in gamma '-Ni3Al intermetallics

Nanoscale gamma precipitates in primary microscale gamma' precipitates of Ni-alloys have been recently observed in experiments. Nanoscale gamma precipitates have been one of the potential factors changing the dislocation motion in primary gamma' precipitates and affecting mechanical properties of Ni-alloys. In this work, the dependency of the interaction between a superlattice screw dislocation and the spherical gamma-Ni precipitates in gamma'-Ni3Al intermetallics on the sizes of the gamma precipitate is studied via molecular statics simulations. The calculated external stress, morphology of superlattice screw dislocation, and energy states show that the stress necessary to cut through the precipitate is significantly dependent on the interface between the gamma precipitate and gamma'-matrix as well as on the antiphase boundary (APB) energy; the interface between the gamma precipitate and gamma'-matrix inhibits the superlattice dislocation during cutting into the gamma precipitate, whereas the APB expansion hinders the cut-out action. Among the examined cases, a precipitate of approximately 3 nm in diameter is found to require the largest stress to cut through. We show the origin of interaction between superlattice screw dislocation and gamma precipitates in gamma'-matrix from the atomic and energetic perspectives.