A coupled crystal plasticity FEM and phase-field model for crack evolution in microstructures of 7000 series aluminum alloys

A coupled crystal plasticity-phase field (CP-PF) model is developed in this paper for analyzing crack nucleation and propagation in polyphase-polycrystalline microstructures of Aluminum 7000 alloys. The model explicitly represents elastic and plastic anisotropies, tension-compression asymmetry, and the crack surface topology in the material. The phase field model incorporates a regularization length-scale l(c) that controls the sharpness of the phase-field approximation to the discrete crack. A novel adaptive wavelet-enriched hierarchical FE augmentation is developed for the coupled CP-PF model. It has the unique capability of optimally resolving high gradients in the phase field order parameter s near the crack surface. Parametric studies are conducted with one and two precipitate RVEs in an Al matrix to understand the effect of microstructure and loading on crack evolution. Finally, an image-based microstructural model is developed and simulated to predict crack initiation, growth, and propagation in microstructures of the Al alloy Al7075-T651.