Rapid Recrystallization and Mechanical Properties Improvement of Ti-6Al-4V during Electrothermal Treatment

The formability and plasticity of titanium alloys at room temperature are relatively poor, and heat treatment is often used to regulate the microstructure of titanium alloys to obtain excellent comprehensive properties. However, a challenge with traditional resistance furnace heating is its low efficiency, prolonged heating time, severe oxidation, and coarse grain structure, which make it difficult to achieve a good balance between high strength and sufficient ductility. In this study, electrothermal treatment was conducted on Ti-6Al-4V sheets to investigate the mechanical behavior and microstructural evolution under different direct current densities. The results indicated that, with the increase in current density, the strength of Ti-6Al-4V alloy first increased and then decreased. Correspondingly, the alpha phase size decreased first and then increases, and the initial strip morphology changed to equiaxial morphology. The proportion of large-angle grain boundary (HAGB) increased. The athermal effect of the current promoted recrystallization, and the thermal effect facilitated the growth of recrystallized grains. Additionally, with the increase in current density, the texture strength was continuously reduced. Compared with the initial alloy, the alloys after electrothermal treatment achieved excellent synergy between strength (949 MPa tensile strength) and ductility (11.66% elongation).