Construction of multi-scale heterostructures via localized electropulsing treatment for synergistic strength-ductility enhancement in Cu-Ti alloys

Heterostructured materials achieve excellent strength-ductility matching through the cooperative stress-strain distribution mechanism of soft and hard phases. Inspired by the periodic arrangement of hard and soft zones in biological armors which can achieve load redistribution and impact dissipation, this work successfully constructed a biomimetic armor structure of multi-scale heterostructures (MSH) in Cu-2.9 wt.% Ti alloy sheets based on the localized electropulsing treatment (LEPT) technology. Room-temperature tensile testing combined with Digital Image Correlation (DIC) analysis revealed that the heterostructure reduces strain concentration during deformation. This results in a ∼64% enhancement in ductility compared to conventionally aged samples, with only a ∼14% reduction in strength, leading to a 36% increase in the strength-ductility product (UTS × EL). The retained extensive soft zones provide a foundation for good ductility, while the heterogeneous deformation-induced (HDI) strain hardening and HDI strengthening resulting from deformation incompatibility significantly enhance the alloy's strength, effectively suppress localized necking, and enable sustained, uniform deformation. This multi-scale heterostructure significantly enhances the strain hardening capacity of the material, not only providing a novel paradigm for designing high-strength, high-ductility alloys, but also offering theoretical basis and technical support for the flexible design and targeted regulation of heterostructured materials.