High dislocation density formation in metallic materials by ultra-intense nanopulsing electric current

Abstract

We report a novel material processing using ultra-intense nanopulse electric current to achieve unprecedentedly high dislocation densities in metallic materials. By applying electrical current nanopulses with intensities exceeding several 10¹⁰A/m², we observed a high-density dislocation formation across with multiple scales, including micro-, sub-micrometer, nano- and sub-nanometer scales. Unlike conventional deformation or thermal processing, this method enables the creation of dislocation densities beyond the limits of cold-worked metals, reaching up to 10¹⁸/m² at the nanoscale. Our results indicate that while microscale dislocations reach densities $\lesssim$10¹⁵/m², a threshold typical for heavily cold-worked metals and alloys, nanoscale screw dislocations achieve densities around 10¹⁸/m². This remarkable enhancement in defect density suggests a new pathway of tailoring mechanical and physical properties of metallic materials. We think this increase stems from significant stress concentration at grain boundaries (GBs) due to electron wind forces, which substantially heightens shear stress levels within grain interiors, particularly near lattice defects. Additionally, we demonstrate that higher pulsing frequencies lead to a greater degree of dislocation formation, revealing a frequency-dependent mechanism that enhances lattice distortion through localized shearing. Our findings suggest that ultra-intense nanopulse electric current promotes the significant generation of dislocations, which could significantly alter material properties, paving the way for advanced defect engineering in metallic materials. This innovative approach holds promise for applications in high-strength materials, microelectronics, and functional materials where defect engineering plays a critical role.