Strengthening and toughening mechanisms in heterostructured laminates revealed by a phase field-enhanced crystal plasticity simulation

Heterostructured (HS) materials exhibit excellent mechanical performance, achieving strength-ductility synergy by combining high strength with enhanced fracture resistance under large deformation. Hetero-deformation-induced (HDI) hardening and strain delocalization play a central role in governing the mechanical response of HS materials. However, existing models often fall short in addressing these aspects. In this work, a coupled framework integrating strain-gradient crystal plasticity and phase field model is developed. The interface-dominated HDI hardening in HS laminates is handled by introducing a heterogeneity coefficient into the back stress. The phase field model accounts for defect energy-driven fracture process and accurately represents the material’s ductile fracture behavior by accounting for effects of microstructure on crack initiation and propagation. Simulation results for HS laminates align well with experimental results and reflect the distribution of geometrically necessary dislocations and back stresses at interfaces between regions with dissimilar microstructure. Crack initiation and propagation are accurately described, providing valuable insights into fracture processes. The strength-ductility-related mechanical performance at large deformations is evaluated in terms of sustained load-bearing capacity following crack initiation. This enables comparison of mechanical stability across different HS laminate architectures. The proposed framework offers a predictive tool for microstructure-informed design and optimization of heterostructured materials.