Electrically-assisted Micro-forming Process Of Ultrafine-grained Pure Titanium For Shaft Parts

With the rapid development of the electronic industry,people's pursuit of lightweight and miniaturization is getting higher and higher,and the market demand for micro and small parts also increases accordingly.Shaft parts occupy an indispensable position in the industrial development,the general performance requirements of shaft parts are relatively high,whether in the transmission or support,will be subject to greater stress,sometimes also need to have a higher wear resistance and corrosion resistance.Ultrafine pure titanium materials obtained by violent plastic deformation have excellent mechanical properties,and their strength is equal to that of ordinary titanium alloys,and they have better biocompatibility and non-toxicity than titanium alloys when applied to biomedicine.The traditional isothermal forging method of shaft parts has the disadvantages of too low heating efficiency and large energy consumption,which are not in line with the production concept of modern green manufacturing and energy-saving manufacturing.In this paper,based on the high resistivity and poor thermal conductivity of pure titanium materials,the method of microforming assisted by current is put forward.By directly adding current to the pure titanium blank,the blank is heated to the forming temperature in a very short time to realize the rapid energy-saving forming process.This topic mainly studies the ultrafine crystal pure titanium thin current auxiliary shaft parts forming process,the current of pure titanium material auxiliary micro compression deformation behavior are studied,by adopting the combination of finite element simulation and actual experimental method,choose the suitable way of load current,achieve ultra-fine crystal pure titanium quality of slender shaft parts manufacturing.The mechanical properties of ultrafine and original crystal pure titanium materials were investigated by microcompression test method assisted by current,and the influence mechanism of current on the deformation process of compressed samples was analyzed.The results show that the flow stress decreases with the increase of current density.In the constant current mode,the current at both ends of the sample decreases with the increase of the deformation degree.Under the constant pressure mode,the nominal current density of the sample increases with the increase of the deformation degree.In the upflow mode,the flow stress of pure titanium material begins to decline after the strain reaches a certain value with the increase of the deformation degree of the sample.By using the deform-3d finite element simulation software,the forming experiment of shaft parts is simulated under different power modes.It is found that under constant current and pressure mode,the blank temperature decreases too fast,resulting in higher final forming load.However,under the upflow mode,the lowering speed of blank temperature can be significantly reduced,the softening effect of blank is better,and the final forming load is lower.In addition,the velocity field,strain field and temperature field of the blank during the deformation process are analyzed,which is of guiding significance to the actual process test.The experimental results of current-assisted forming technology for slender shaft parts show that the temperature of the blank decreases gradually with the increase of deformation degree.Under the same maximum forming load,the forming effect of upflow mode is the best,the filling quality of steps and rounded corners is better,and the surface oxidation degree is lighter.However,under the maximum forming load of 7000 N,the filling effect of constant current and constant voltage mode is not ideal,and the oxidation in the middle region is more serious.Therefore,the forming effect is the best when the rising current mode is selected.According to the experimental results of friction and wear performance of shaft parts,the wear resistance of ultrafine crystal shaft parts is better,and the friction coefficient and wear amount decrease with the increase of rotating speed.With the increase of load,friction coefficient and wear amount increase.