Molecular dynamics simulation of dislocation nucleation and motion at γ/γ′ interface in Ni-based superalloy

Molecular dynamics simulations are conducted on the dislocation behavior at the apices and edges of cuboidal Ni3Al precipitate in a pure Ni matrix, or the idealized gamma/gamma' microstructure in a Ni-based superalloy. A tensile simulation of the [001] direction is implemented with a periodic cell that has eight cubic precipitates in order to investigate the nucleation site of dislocation in the idealized microstructure with no defects other than the gamma/gamma' interfaces. The effect of residual internal stresses on the stability of the interfaces is also discussed. Other simulations are conducted on the behavior of edge dislocations nucleated from a free surface and proceeding in the gamma matrix toward gamma' precipitates under shear force. Dislocation pinning at gamma' precipitates, bowing-out in the gamma channel, pile-up and nucleation of superdislocation in the gamma' precipitate are simulated and inspected in detail. Discussions on the size of the gamma/gamma' microstructure and the sharpness of the edge of the gamma' precipitate are also presented. (C) 2002 Elsevier Science Ltd. All rights reserved.