Heterogeneity-Driven Strengthening and Hardening in Heterostructured Materials: Modeling and Simulation Across Length Scales

Heterostructured metals and alloys are designed with spatial variations in strength and hardening that produce synergy beyond the rule of mixtures. This review surveys face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP) systems, including architectures formed or modified by rolling and related severe plastic deformation routes, and examines them under tension, compression, and shear. Across material classes, mechanical incompatibility between hetero-zones drives stress partitioning and plastic strain gradients that store geometrically necessary dislocations near zone boundaries. The associated internal back and forward stresses sustain work hardening, delay instability, and influence localization and damage initiation. We evaluate continuum, crystal plasticity, dislocation-based mesoscale, and atomistic approaches by whether they predict these internal fields and whether they are validated against internal-field measurements. Key observations are that predictive models require physically identifiable intrinsic length scales, experimentally constrained interface laws, and careful separation of mechanisms to avoid double-counting when gradient and kinematic terms coexist. Major gaps remain in parameter identifiability for multi-zone and nonlocal formulations, in transferability across processing routes and loading modes, and in community benchmarks that couple well-characterized microstructures with multimodal measurements. Recommendations are provided for validation targets and benchmark campaigns to accelerate predictive design.