Anisotropic phase-field crystal plasticity modelling of fracture in nickel-based superalloy

Abstract

Accurately predicting anisotropic damage evolution in crystalline metals remains a challenging topic due to the multiscale nature of fracture. Microstructures play a critical role in influencing crack deflection at the macroscale. To study the relations among anisotropic deformation, crack initiation and propagation, an anisotropic phase-field crystal plasticity model has been developed for nickel-based superalloys. This model differs from conventional approaches in formulating the critical energy release rate as a function of preferentially activated slip or cleavage planes, rather than merely considering it as an isotropic quantity. This development not only allows effective representation of crack initiation due to local anisotropy introduced by slip activation, but also enables a more accurate representation of crystallography-dependent fracture behavior.

The performance of proposed method will be demonstrated to characterize crack initiation and propagation in nickel-based single-crystal and polycrystal superalloys. The proposed anisotropic phase field method has been found to be consistent with generalized maximum energy release rate criterion. The findings highlight the significant influence of crystallographic orientation on the crack formation in single crystals. Increased geometrically-necessary dislocation (GND) density has been observed along the activated slip directions, particularly for those near the crack tip. The model capability has also been exhibited in characterizing crack deflection within polycrystalline microstructures. The model is further verified against available experiments reported in recent literatures, by virtue of simultaneously comparing the stress-strain response and crack growth.