Responses Of Microstructure And Mechanical Properties Of TA15 Titanium Alloy Treated By Pulse Current

As a new forming method,the current assisted forming has electroplastic effect when applying current to metal or other alloys to improve material properties and productivity and efficiency of parts.TA15 titanium alloy has excellent comprehensive mechanical properties,but is difficult to process.The current assisted microforming shows its unique advantages.This research from the perspective of thermal-mechanical,using pulse current processing experiment and current auxiliary micro tensile experiment,and the pulse current on microstructure and mechanical properties of TA15 titanium alloy at response law,analyzes the pulse current processing organization evolution,pulse current processing principle of crack healing,revealing the pulse current auxiliary micro tensile mechanical behavior and response mechanism.It provides a theoretical basis for current assisted microforming technology of titanium alloy.The microstructure evolution experiments were carried out to analyze the diffusion,recovery,recrystallization and phase transformation processes of metal atoms in titanium alloy under pulsed current excitation,as well as the evolution law of grain orientation in the material after pulsed current treatment.Compared with isothermal treatment at the same temperature,the experimental results show that the current excitation accelerates the transition from ? phase to ? phase,and the ? phase supersaturates into acicular martensite ?' phase during the subsequent rapid cooling process.The effects of pulse current parameters and pulse treatment time on crack healing of titanium alloy were studied.The principle of crack healing in pulse current treatment was revealed,and the methods of suppressing and curing microscopic defects in the process of pulse current microforming were proposed.The experimental results show that the appropriate pulse current parameters can effectively heal the cracks,and the bend effect and Joule heating effect are the main reasons for the crack healing.The effects of current density,pulse frequency,duty cycle,strain rate and other parameters on the mechanical properties and microstructure of TA15 titanium alloy were investigated by high frequency pulse current assisted microtensile experiments.With the increase of current density and pulse duty ratio and the decrease of strain rate,the flow stress and plasticity of the material decrease,but the influence of pulse frequency in a certain range is small.The mechanical behaviors under different power densities were studied by low frequency pulsed current assisted microtensile experiments.The results show that the flow stress drop increases linearly with the power density,and the electroplasticity under pulsed current can significantly improve the formability of the material.