Abstract:By applying different current frequencies during the tensile process of the aerospace TC4 titanium alloy, the flow stress of the material is increased and its maximum yield strength is reduced. The microstructural evolution of the material after electrification and the fracture morphology of the samples were observed. The influence of the electric-assisted forming process on the tensile process was analyzed in combination with the tensile test results. The experimental results show that with the increase in pulse current density, the content of the α phase decreases significantly, while the β phase content increases substantially, and the grain size begins to increase. A small amount of martensitic phase suffers transformation during cooling, resulting in fine acicular α′ phase. As the current density further increases, the primary α phase disappears completely, the β phase grows further, and the size of the transformed α′ phase increases. During tensile deformation, the sample temperature rises sharply at the moment when current is applied. It continues to increase during the tensile process, with rising increment until it reaches a peak value at the moment of fracture. The peak temperature increases with the rise in current density and pulse frequency. As the current density increases, the flow stress of TC4 titanium alloy gradually decreases, and its ductility improves. SEM and TEM results show that with the increase in current density, the dimples in the tensile fracture surface of TC4 titanium alloy sheets become significantly deeper, presenting a honeycomb-like appearance, with tear ridges around the dimples, indicating a typical ductile fracture feature. Compared with that after high-temperature and room-temperature tensile tests, the dislocation density inside the material after electric-assisted tensile tests is significantly reduced, with dislocations appearing more straight and some dislocations orderly aligned in a certain direction, indicating that pulse current promotes dislocation motion.