Research On Electro-assisted Power Spin Forming Mechanism And Process Of TA2 Pure Titanium Sheet

Titanium and titanium alloys have a wide range of applications in aerospace,weaponry,petrochemical and biomedical fields due to their excellent comprehensive properties.The existing manufacturing methods of titanium and titanium alloy components have complicated processes,poor product reliability,and long manufacturing cycles.The CNC spinning technology is an advanced flexible plastic forming process and has unique advantages in forming thin-walled hollow rotating components.In order to solve the spinning problem of titanium and titanium alloys at room temperature,this paper proposes a new electro-assisted CNC spinning forming technology for difficult-to-deform materials and designs a complete set of experimental equipment.The research method combining theoretical analysis,numerical simulation and experiment was used to study the deformation mechanism,forming defects,numerical simulation,process experiment and micro-properies of TA2 pure titanium components during electro-assisted spinning.Which provides theoretical and process references for the practical application of this technology.The main research contents of this article are summarized as follows:(1)A complete electro-assisted spinning forming experimental device was designed and preliminary experimental verification was performed.The results show that the technology is feasible and easy to control.(2)The spinning deformation mechanism of TA2 pure titanium sheet was studied.The electroassisted spinning forming of the curved mother linear component is a type of shear deformation.The wall thickness changes follow the law of sine,and different wall thickness deviations have different effects on the type of material deformation.Meanwhile,a simplified analysis model of stress in the spinning deformation zone was established,and the mechanism of the effect of current on the fracture of pure titanium spinning components was analyzed.The effects of different wall thickness reductions and its deviation rates on the stress changes,material flow,and forming defects of the components were revealed.(3)The thermo-electric coupling numerical model for electro-assisted spinning forming of TA2 pure titanium sheet was established.The effects of different process parameters on the surface potential and temperature distribution of titanium sheet were analyzed.It is found that the current mainly flows from the center of the titanium sheet in a straight line to the contact point of the tool head,the temperature is mainly distributed in the contact point,and the temperature diffusion phenomenon is weak.Considering the temperature of the deformation zone,processing efficiency and sheet oxidation,etc.,a 400 A current,a medium-sized tool head and a large current loading area should be used during spinning.(4)The effects of process parameters such as current intensity on the forming limit,dimensional deviation,deformation springback and surface quality of pure titanium sheets was studied.The results show that the current intensity and the feed rate of the roller are the most important process parameters.The constant linear velocity mode of the spindle is beneficial to the uniform surface temperature and texture distribution of the titanium sheet.Experiment results have found that molybdenum disulfide is an ideal high-temperature conductive lubricant,which can significantly improve the surface quality of spinning components.(5)The effect mechanism of wall thickness reduction and current intensity on the microhardness,metallographic structure and texture evolution of pure titanium spun compoents were studied.It was found that gradually elevated current intensity caused a slight decrease in the microhardness of the components,and the deformeded ?-phase grains dynamic recrystallized to form more regular and refined grains.EBSD experimental results show that the current changes the initial ?0 0 0 1? basal texture of pure titanium to?1 0 (?) 0? and ?0 0 0 1? basal texture,and further increases the proportion of higher angle grain boundaries.It was found that when the current destity increased from 400 A to 600 A,the pole figure grain orientation evolved from a band-like distribution to a symmetrical distribution about the center.