Deformation Behaviour And Its Mechanism Of TC4During Electroplastic Drawing

TC4titanium alloy has to be deformed at elevated temperature during the rods, pipes, and wire production because of its low deformability and high strain hardening exponent. However, TC4would likely react with oxygen at a high temperature, leading to the instability of product quality. Therefore, it is important to realize the cold deformation of TC4. In the present work, the electroplastic drawing technology was applied on TC4. The effect of the electropulsing treatment on the deformation resistance during deformation process was investigated. The microstructure and the mechanical property evolution after electroplastic drawing were also studied systematically. In addition, the recrystallization and the phase transition behaviour of TC4under high energy electropulsing treatment were also investigated. The results indicate that:(1) The electropulsing can reduce the drawing force during the TC4cold drawing due to the promotion of dislocation slip. The deformation resistance of the wire decrease with the electropulsing current density. When the maximum current density reaches to240A/mm2, the drawing force decreases by24%compare with conventional cold drawing.(2) The strain hardening of TC4wire is restricted by electroplusing treatment during cold drawing as the electroplusing inhibits the dislocation pile-up. In addition, the microstructure is more homogeneous after electroplastic cold drawing. The residual stress of the central part of the wire is low, as a result, the formation of the nib fracture is restricted.(3) The texture evolution after electroplastic drawing indicates that:the prismatic <a> slip is promoted by electropulsing, whereas the pyramidal <c+a> slip that causes the rotation of c-axis is restricted. Deformation with c-components of the material under electropulsing treatment is accommodated by grain boundaries sliding.(4) After treated by electropulsing, the recrystallization grains form at the grain boundary. Due to the very short treating time and high nucleation under electropulsing, the recrystallized grains have no enough time to grow. The recrystallized grains are formed with finer-grain size and accumulated near the grain boundary. During the recrystallization process, the deformation storage energy is exhausted. As a result, the strength of the wire decreases and the plasticity increases. (5) The α2-To3Al phase with the oval morphology is formed in the a grains after treated by electropulsing. The result indicates that the electroplusing enhance the precipitation rate of TC4attribute to the electromigration under the electric field.