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

Abstract

We proposed a back force model for simulating dislocations cutting into a c 0 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 c/c 0 interface covered by an interfacial dislocation network. The former simulation shows that dislocations penetrate 0749-6419/$ -see front matter Ó International Journal of Plasticity 22 (2006) 713-723into a c 0 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 c 0 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.

Modelling plastic deformation in a single-crystal nickel-based superalloy using discrete dislocation dynamics

“…A back-force model (Yashiro et al 2006) was introduced to simulate shearing of the γ′ precipitate by a series of superdislocations. The leading and trailing dislocations form a superdislocation, separated by an antiphase boundary (APB).…”

Discrete dislocation dynamics modelling of mechanical deformation of nickel-based single crystal superalloys

“…All these models are formulated within a continuum framework. Although some interactions between the dislocations and the microstructure may be considered by the strain gradient (Busso et al, 2000) or statistic laws (Fedelich, 1999;2002), these methods are limited in the study of the interaction between dislocations and the superalloy microstructure (Yashiro et al, 2006), as the statistic laws may not be appropriate at the microscale or nanoscale of precipitates and channels.…”

3D DDD modelling of dislocation–precipitate interaction in a nickel-based single crystal superalloy under cyclic deformation

“…superdislocation [15,16]. Based on these experimental observations, a back-force model suggested by Yashiro et al [10] was applied to simulate precipitate shearing by series of superdislocations explicitly. When a leading dislocation cuts into a precipitate, it leaves an antiphase boundary (APB) on the slip plane with a back force F b (equals to antiphase boundary energy χ APB ) acting on it.…”

“…In grains with a bimodal precipitate, the simulated mechanical behaviour (such as stress-strain behaviour, PSBs, dislocation densities and cyclic response) fell between the above two cases. Yashiro et al [10] studied dislocation shearing into γ′ precipitates by applying a back-force model, and the model was used to explore the dependence of precipitate-shearing resistance on the dislocation spacing in the interfacial dislocation network for nickel-base superalloys.…”