Discrete dislocation dynamics simulation of cutting of γ′ precipitate and interfacial dislocation network in Ni-based superalloys

We proposed a back force model for simulating dislocations cutting into a γ′ precipitate, from the physical viewpoint of work for making or recovering an antiphase boundary (APB). The first dislocation, or a leading partial of a superdislocation, is acted upon by a back force whose magnitude is equal to the APB energy. The second dislocation, or a trailing partial of a superdislocation, is attracted by the APB with a force of the same magnitude. The model is encoded in a 3D discrete dislocation dynamics (DDD) code and demonstrates that a superdislocation nucleates after two dislocations pile up at the interface and that the width of dislocations is naturally balanced by the APB energy and repulsion of dislocations. The APB energy adopted here is calculated by ab initio analysis on the basis of the density functional theory (DFT). Then we applied our DDD simulations to more complicated cases, namely, dislocations near the edges of a cuboidal precipitate and those at the γ/γ′ interface covered by an interfacial dislocation network. The former simulation shows that dislocations penetrate into a γ′ precipitate as a superdislocation from the edge of the cube, when running around the cube to form Orowan loops. The latter reveals that dislocations become wavy at the interface due to the stress field of the dislocation network, then cut into the γ′ precipitate through the interspace of the network. Our model proposed here can be applied to study the dependence of the cutting resistance on the spacing of dislocations in the interfacial dislocation network.