Mr. Haoyu Huang - M.Sc. Candidate
08/10/2026
Zoom
13:30 - Jerusalem time / 18:30 - Beijing time
Using periodic electric current pulses, i.e. electropulsing (EP) treatment, to stimulate microstructure evolution has been drawing increasing attention due to its potential to replace traditional thermal treatment. The significantly improved kinetics under EP treatment should originate from the accelerated diffusion processes. However, quantitative determination of EP-enhanced diffusivity remains scarce. In this project, we use well-defined diffusion couple to study the influence of EP parameters and current polarity on the variation of inter-diffusivity.
Cu-Ni diffusion couples containing two interfaces with opposite orientations relative to electron flow were fabricated by field-assisted sintering technique (FAST) bonding of a brass/Ni/Cu/Ni/brass stack (550 °C, 2 h, 40 MPa) and sectioned into strip specimens containing two Cu-Ni interfaces. The samples were then subjected to coupled thermal and EP treatments using 1 ms square-wave pulses (1100 A/mm², 24 h, 350-500 °C), with furnace-only references. The resulting Cu and Ni concentration profiles across both interfaces were characterized by SEM/STEM-EDS and analyzed in terms of interdiffusion behavior, using Matano plane aligned data with forward simulation, Sauer–Freise method and Hall method. Interfacial microstructures were examined via OM, TEM and TKD.
Quantitative evaluation of the concentration profiles showed that EP treatment increased interdiffusivity and decreased the activation energy at the Cu-Ni interface where electron flow was aligned with Ni-to-Cu transport, whereas no corresponding enhancement was detected at the oppositely oriented interface. This establishes a clear polarity dependence of EP-enhanced interdiffusion. To rationalize the directional asymmetry, the possible effects of electron wind force, localized Joule heating and diffusion induced recrystallization were assessed. The analysis attributes the dependence to the divergence of the electromigration-driven vacancy flux.