Wu Kaiwei, a master’s student from the Class of 2026 at the SJTU Paris Elite Institute of Technology (SPEIT), has published a research article as first author in the flagship international journal in solid mechanics, Journal of the Mechanics and Physics of Solids (JMPS). The paper is entitled: “A Multiscale Investigation into the Electroplastic Effects in Copper: Experiments and Crystal Plasticity Modeling.”
This study systematically reveals the multiscale mechanical behavior and microscopic deformation mechanisms of metallic materials represented by pure copper under electroplastic effects, and provides an in-depth discussion of long-standing controversial scientific issues in this field. Shanghai Jiao Tong University is the first affiliated institution of the paper. Dr. Sun Xiaochuan (postdoctoral researcher at the School of Materials Science and Engineering), Associate Professor Shi Qiwei (SPEIT), and Professor Wang Huamiao (Shanghai University) are co-corresponding authors.
Article Overview
In this work, pulse current-assisted tensile experiments were conducted on pure copper under strictly controlled temperature conditions. Cold air cooling and infrared thermometry were employed to maintain the sample temperature close to room temperature, thereby highlighting non-thermal effects.
The experimental results show that under electrically assisted loading, the stress–strain curve exhibits characteristic local fluctuations. Within a single pulse, the stress response undergoes two sequential stages: a “rapid drop” followed by a “gradual drop.” Meanwhile, the macroscopic flow stress and strain hardening rate decrease significantly with increasing current density.
Through large-area EBSD, dual-beam TEM, and high-resolution EBSD characterization, it was found that electroplasticity does not activate non-close-packed slip systems, and the <111>//RD texture intensity remains essentially unchanged. However, the total dislocation density is significantly reduced, mainly due to the recovery of statistically stored dislocations (SSD), while the geometrically necessary dislocation (GND) density remains nearly unchanged.
Stress response of samples under different pulse current densities
Histograms of GND density, KAM analysis, and quantitative estimation of SSD density reduction in deformed samples under different pulse currents
Furthermore, based on the elastic-viscoplastic self-consistent (EVPSC) framework, a force–electromagnetic coupled crystal plasticity model (EC-EVPSC) was established. By introducing the effect of electric current on lowering short-range energy barriers (modifying the activation free energy in the Orowan equation), the model describes the “rapid drop.” In addition, by incorporating the influence of current on dislocation core energy into the Kocks–Mecking type dislocation evolution equation, the dislocation multiplication coefficient and recovery energy barrier are modified to describe the “gradual drop.”
Experimental (Exp.) and simulated (Sim.) stress–strain curves under different pulse currents
With only two current-related parameters, the model successfully reproduces the macroscopic stress–strain curves, local stress fluctuations, semi-quantitative dislocation density evolution, and qualitative texture evolution under different current densities. It has also been thoroughly validated using independent experimental cases (70 A/mm²) and different pulse parameters (1 Hz, 10% duty cycle).
Schematic diagram of the three-stage mechanism
This study not only further clarifies the physical origin of electroplasticity in copper but also provides reasonable reinterpretations of controversial phenomena reported in the literature. The authors point out that the weak electroplastic effect observed in some copper experiments may be due to early dislocation annihilation during the preloading stage. The absence of electroplasticity in lead at low temperatures is attributed to its superconducting state (consistent with BCS theory), which suppresses electron–dislocation scattering and magnetoplastic mechanisms. Differences in electroplastic responses among metals are related to intrinsic properties such as electron relaxation time, indicating that the electroplastic mechanism is material-dependent.
Full text link：
https://doi.org/10.1016/j.jmps.2026.106597
Overview of Research Collaboration
This work is the result of international scientific collaboration, involving researchers from multiple institutions across four countries. Wu Kaiwei not only served as one of the main contributors to the scientific content but also undertook responsibilities in research organization, team building, and coordination, demonstrating the international competence of SPEIT students in collaborative research.
Domestic institutions: SJTU Paris Elite Institute of Technology (SPEIT), School of Materials Science and Engineering, School of Mechanical Engineering (Shanghai Jiao Tong University); School of Mechanics and Engineering Science (Shanghai University); School of Mechanics and Engineering Science (Peking University).
International institutions: Centre des Matériaux (Mines Paris-PSL), Centre de Mise en Forme des Matériaux (France); Max Planck Institute for Sustainable Materials (Germany); Faculty of Engineering, Lancaster University (UK).
Main Research Supervisors
Sun Xiaochuan is a postdoctoral researcher at the School of Materials Science and Engineering, Shanghai Jiao Tong University. He obtained his bachelor’s, master’s, and doctoral degrees in Mechanical Engineering from Shanghai Jiao Tong University. He has published 18 SCI papers in journals such as Nature Photonics, Journal of the Mechanics and Physics of Solids, Acta Materialia, and International Journal of Plasticity.
Shi Qiwei is an Associate Professor at the SJTU Paris Elite Institute of Technology (SPEIT). He has led multiple projects funded by the National Natural Science Foundation of China (general and youth programs) and received support from EDF and TESCAN. He has published over 40 papers in journals such as Journal of the Mechanics and Physics of Solids, Acta Materialia, International Journal of Plasticity, and Materials Characterization.
Wang Huamiao is a Professor at the School of Mechanics and Engineering Science, Shanghai University. He has led multiple research projects, including general and regional programs of the National Natural Science Foundation of China, and has published over 100 papers in journals such as Nature Photonics, Nature Nanotechnology, Nature Communications, Journal of the Mechanics and Physics of Solids, International Journal of Plasticity, and Materials Characterization.
Samuel Forest is a Professor at Mines Paris. He was elected a member of the French Academy of Sciences in 2022. Professor Forest is an internationally renowned expert in solid mechanics. He has received prestigious honors such as the Huy Duong Bui Medal from the French Academy of Sciences and the CNRS Silver Medal. He has long been dedicated to developing the theoretical framework of Generalized Continuum Mechanics and has led systematic research on plastic deformation, damage, and fracture mechanisms in polycrystalline materials, metal foams, and porous media. His work has demonstrated outstanding application value in lifetime prediction and performance optimization of critical engineering components. He also serves as Secretary General of EUROMECH, a member of the ICTAM Congress Committee, and holds editorial positions (Editor/Associate Editor) in several major international journals.
Journal Introduction
Founded in 1952 by Rodney Hill, one of the key founders of modern solid mechanics, the Journal of the Mechanics and Physics of Solids (JMPS) is a long-established and highly recognized flagship journal in the field of solid mechanics. The journal adheres to its core principle of publishing “research of the highest quality with lasting value” and encourages authors to elaborate on the profound significance and impact of their work on the development of the mechanics discipline.