The role of layer strength ratio in enhancing strain hardening and achieving strength-ductility synergy in heterostructured materials

Abstract

Heterostructured materials, characterized by distinct zones with varying mechanical properties, offer a promising strategy to overcome the traditional strength-ductility trade-off in metallic materials. In this study, we focus on heterostructured materials composed of hard and soft metallic layers, investigating the effect of the layer strength ratio (R) on strain hardening in these materials. Using a combination of experimental techniques, crystal plasticity finite element (CPFE) simulations, and discrete dislocation plasticity (DDP) simulations, we explore how R influences the accumulation of geometrically necessary dislocations (GNDs) and the associated stress field at the hetero-zone boundary (HB). Our findings reveal that deformation inhomogeneity between the soft and hard zones generates significant strain gradients near the HBs, leading to enhanced strain hardening through intensified dislocation pile-up and long-range internal stress. Increasing the layer strength ratio R amplifies the deformation inhomogeneity near the HBs, resulting in substantial strain hardening. Additionally, HB density is shown to be another tunable parameter that, when optimized, can significantly enhance strain hardening. This work establishes a quantitative framework for understanding the relationship between layer strength ratio R and strain hardening, offering valuable insights for optimizing the strength-ductility synergy in heterostructured materials.