A modified dislocation density-based model of 30CrMnSiA considering the coupling effect of electroplasticity and grain refinement during the pulsed current-assisted plane strain deformation

The large deformation of difficult-to-deform metal under pulsed currents involves the coupling effect of grain refinement and electroplasticity, making it challenging to capture the flow behavior accurately during severe plastic deformation. To develop a highly accurate constitutive model that accounts for the coupling effect, a current-assisted plane strain compression (CAPSC) test of 30CrMnSiA was carried out, using a peak current density (Jp) range of 0–30 A mm−2 and duty ratio (d) of 0–20%. A microstructural observation was also performed via the EBSD test on the specimens after the CAPSC test. The result indicates that the true stress decreases significantly with increased Jp and d, descending to a stable value of 13% under high Jp and high d regions. Pulsed current accelerates grain refinement, promoting the transition from low-angle grain boundaries to high-angle grain boundaries through the recovery mechanism. Fine grain sizes increased from 31.7 to 45.5% in the pulsed-current condition compared to the non-current condition. Based on the above discovery, a physical-based constitutive model frame was proposed to characterize the independent evolution and transformation of dislocation density at the grain boundary and interior. Besides, the current density is also coupled into the model as an influence term of the material parameters to capture the influence of electroplasticity on grain refinement. Comparing the test stress to the predictive stress reveals that the model accurately predicts the CAPSC stress of 30CrMnSiA with a correlation coefficient of 0.974 and an average relative error of 4.56%.