Significant mechanical softening of copper under coupled electric and magnetic stimuli

The mechanical reliability of metallic components is vital for the stable operation of electrical equipment, especially for those used in ultra-high voltage transmission and electromagnetic launching, where metallic materials inevitably suffer from high-density current and strong magnetic field. However, little has been known about the mechanical behavior of metals under the electric-magnetic coupling stimuli. Here, by performing quantitative electromechanical tests under the built-in magnetic field inside transmission electron microscope, we found that copper, one of most commonly used conductive metals, can be significantly softened by the coupled electrical-magnetic stimuli, manifested as notable yield strength drop by five-times and obvious creep deformation at room temperature. A plausible mechanism behind the unusual softening, local-Lorentz-force-assisted dislocations depinning, has been proposed. Our results shed new light on understanding the deformation-induced failure of metals served in electromagnetic environments, and also inspire a new me-chanical processing way for reshaping metals at much lower loads and temperatures.