A Study on the Mechanism of the Effect of Low‐Frequency High‐Density Pulse Current on the Strength and Ductility of TC4 Titanium Alloy

The electrically assisted forming technique has attracted significant attention in recent years as an effective method for enhancing the formability of TC4 alloys. It has been demonstrated that localized overheating during the tensile deformation process induces premature melting and fracture of the specimen, thereby reducing the material's ductility. This study addresses this issue by conducting tensile experiments using high‐density (6000 A, 9000 A) low‐frequency (1 Hz) pulsed currents at various strain rates (19.8, 5, and 0.1 mm min −1 ). The results reveal that the application of electric current can reduce flow stress by 15–44% at lower temperatures. Reducing the strain rate to 0.1 mm min −1 leads to a reduction in the area of cleavage facets on the fracture surface, an increase in the size of dimples, and an improvement in the material's elongation. The application of high‐density pulsed current alters the dislocation structure, facilitating the formation of dislocation walls and dislocation cells. This process accelerates the proliferation of dislocation cells, thereby reducing dislocation entanglement. Dislocations are preferentially distributed along subgrain boundaries, resulting in a decrease in the fraction of deformed grains within the microstructure by ≈30%. First‐principles calculations are employed to validate the experimental observations and further elucidate the electroplasticity mechanism. The application of an electrothermal field is found to reduce tensile stress, in agreement with experimental data. Furthermore, the introduction of electric current lowered the vacancy formation energy of the material from 11.5 eV to 8.2 eV. Charge density difference calculations indicate that, in the presence of an electric field, atomic charges accumulate in the direction of the electric current, resulting in a reduced atomic charge density in the perpendicular direction. Conversely, when a thermal field alone is applied, despite the motion of charges in various directions, the change in charge density remains relatively small. These findings underscore the distinct effects of electroplasticity and thermal influences on the mechanical behavior of materials, providing a partial basis for understanding the microscopic mechanisms underlying the electrically assisted forming process.