Decoupling electroplastic effects and recrystallization kinetics in hardened copper under energy-equivalent pulsed vs. continuous electric fields

Wire drawing induces severe strain hardening in copper through dislocation multiplication, requiring subsequent thermal annealing to restore ductility. Although continuous direct current annealing is conventionally applied, high energy consumption and open-loop control instabilities limit processing efficiency. Electropulse-assisted treatment has emerged as an ultra-fast alternative, yet real-time dynamic current regulation and strict energy-equivalent metallurgical comparisons remain underexplored. This study presents an integrated framework combining closed-loop electropulse generator control, coupled multiphysics thermal-kinetics modeling, and an energy-equivalent physical benchmark ( ∼ 14,900 J) comparing direct current annealing and electropulse-assisted treatment across pulse durations of 35, 70, and 140 μ s on cold-drawn pure copper (99.90%) wires. A custom STM32 microcontroller platform regulates root-mean-square current via peak-current limiting and real-time frequency modulation, maintaining theoretical current accuracy within < 0.16 % and oscilloscope verification within < 6.27 % . The accompanying transient heat balance model accurately predicts surface temperature evolutions ( R 2 = 0.84 – 0.99 ), while a strain-compensated Johnson–Mehl–Avrami–Kolmogorov Arrhenius model captures recrystallization kinetics. Tensile testing reveals that under matched energy input, both direct current annealing and electropulse-assisted treatment successfully recover macroscopic ductility, yielding elongation of 34 – 37 % and ultimate tensile strength (UTS) of 233 – 241 MPa compared to cold-drawn baselines (1% elongation, ∼ 340 MPa UTS). However, a key microstructural divergence emerges: direct current treatment reduces Vickers hardness by 66% and yields 92% recrystallization, whereas electropulse-assisted treatment induces a slight hardness change (＋0.75% to ＋7.8%) and a calculated recrystallization fraction of 38 – 47 % , despite both triggering comparable grain growth ( > 10 μ m ). Electrical resistivity exhibited no statistically significant variation across treated groups ( p = 0.267 ). These results prove that closed-loop electropulse-assisted treatment achieves macro-mechanical restoration comparable to direct current annealing under matched energy inputs while maintaining a distinct sub-microstructural state.