An efficient algorithm of dislocation-precipitate interactions for single crystal nickel-based superalloys within discrete dislocation dynamics and its application

摘要

Abstract In this paper, the discrete dislocation dynamics (DDD) framework for single crystal nickel-based superalloys (SCNBSs) modeling is extended to simulate the superdislocation pairs shearing numerous precipitates more efficiently. An adaptive dislocation segment meshing scheme by specially treating the dislocation segments deposited on the γ/γ′ interfaces is also used to decrease the computational expense. In addition, the MPI parallel algorithm is also realized to increase the computational speed. Through this DDD framework, the size-related plastic response of SCNBSs microcrystal containing collections of precipitates is systematically investigated. Two types of SCNBSs microcrystal samples, one with intact precipitates and the other with partial precipitates truncated by free surfaces, are established for different sample sizes. The influence of the sample size, two types of boundary, and the coherency stress induced by lattice mismatch between the two phases are discussed. The results show that the influence of sample size on the yield strength and the dispersity of stress–strain curves are relatively weak when more than four precipitates across the cross section. And the effect of sample size on deformation mode and the dislocation density is still evident for all the considered sample sizes. For two types (intact and truncated precipitates) of SCNBSs microcrystal samples, the remarkable difference in their mechanical responses and dislocation evolution appears when there is only one precipitate across the cross section. In addition, the misfit stress can significantly change the dislocation distribution in different channels. However, it has less influence on the tensile stress–strain response for the considered tensile loading condition. Our results indicate that to properly characterize the global mechanical behavior of bulk SCNBSs by micro-test, the microcrystal sample should present more than sixteen whole precipitates across the cross section.