Electroplasticity of metallic materials: Electroplastic effect, mechanism, and models

In recent years, the application of electroplasticity in manufacturing components made of hard-to-deform metals, known as electrically assisted (EA) forming, has garnered significant attention. However, due to the varying contributions of the electroplastic (EP) effect (including thermal and athermal EP effects) across different metallic materials, EP behaviors exhibit significant complexity, which limits the improvements in forming performance and forming quality. To facilitate advancements in EA forming technologies, extensive research has been conducted to reveal the EP effect, elucidate EP underlying mechanisms and establish EP constitutive models. This paper reviews the state-of-the-art of the experimental and theoretical progresses in electroplasticity, aiming to provide guidelines for optimizing EA forming processes. Firstly, the regularities of the EP effect evolution in various metallic materials over the past decade are summarized. The parameter dependency and microstructural sensitivity of the EP effect are then delineated. Secondly, a comprehensive assessment of the informed EP theories is conducted from the perspective of momentum and energy transfer during the electron-microstructure scattering process. The application scope, interrelationships, and limitations of various theories are also summarized. Thirdly, the mainstream constitutive modelling methods for predicting EP behaviors of metals are reviewed, which include the physically based methods and the empirically modified methods. Finally, the key challenges and perspectives insights into the field of electroplasticity are presented, focusing on developing experimental decoupling techniques for the EP effect, building “material-parameter-performance” databases of EA deformation, creating a unified theoretical framework of the EP mechanism, and establishing high-fidelity EA constitutive models.