<p>Gradient materials offer a promising pathway to balance strength and ductility through controlled microstructural heterogeneity. In this work, we develop a coupled crystal plasticity-phase field model to investigate the deformation and ductile fracture behavior of gradient-structured metallic composites. The model incorporates grain size-dependent plasticity and simulates crack evolution driven by strain energy. Simulation results show that in pure matrix systems with grain size gradients, increasing the overall grain size leads to reduced strength but improved ductility. This strength-ductility trade-off arises from the interaction between strain delocalization in coarse-grained regions and hardening in fine-grained regions. In particle-reinforced systems, the presence of particles alters stress distribution: smaller particles promote more uniform stress fields and delay damage initiation, whereas larger particles intensify stress and strain energy concentration near fine-grained areas, accelerating crack nucleation and propagation. Crack paths in gradient composites become more tortuous as cracks are forced to bypass particles. The results reveal the critical role of tailoring both grain and particle gradients in regulating the strength-ductility synergy. This study provides a quantitative tool and mechanistic insight into damage evolution in heterogeneous microstructures.</p>