Crack propagation behavior in metal matrix composites: A coupled nonlocal crystal plasticity and phase field modelling

The aluminum matrix composite is known for its lightweight and high strength, while its application is limited in various fields due to its low fracture strain. Configuring reinforcements in metal matrix composites (MMCs) is effective in improving the strength-ductility synergy of metallic materials; however, the underlying mechanisms have yet to be elucidated, and an optimizing strategy is to be explored. This study developed a coupled crystal plasticity (CP) and phase field (PF) model to investigate the toughening mechanisms of MMCs. The CP module incorporates a dislocation flux-based nonlocal model, while the PF module considers the influence of geometrically necessary dislocations (GNDs) on crack initiation and propagation. This coupled model effectively captures the initiation of cracks near the interface due to the accumulation of GNDs at the grain boundary and particle surface. Systematic simulations comprehensively reveal the effects of particle distribution and particle strength on the fracture strain. The findings suggest that arranging particles near grain boundaries improves ductility when particle damage is ignored. However, experimental observations reveal that particles undergo damage during deformation. Only when particle damage is incorporated, does the model accurately reflect the enhanced ductility in scenarios where particles are distributed within the grain interior aligning better with experimental findings. This research enhances our understanding of the damage mechanisms in MMCs and provides valuable insights into their microstructural design.