Experimental Research On Electrochemical Micromachining Of Titanium Alloys Micro-Slits/Grooves In Ethylene Glycol Solution

Titanium alloys are widely used in aerospace,automotive and medical equipment due to small density,high specific strength,heat resistance and corrosion resistance.Micro slits/grooves in titanium alloys have been widely used in many medical micro-implants.Common methods include plastic forming,micro turning,micro grinding,laser beam machining,electrical discharge machining,and electrochemical machining have been adopted to machine micro slits/grooves.However,micro turning,micro grinding and plastic forming are not suitable for machining difficult-to-machine material,there are some problems such as recast layer and micro crack on the surface of workpiece when using laser beam machining and electrical discharge machining.Electrochemical machining has a principle advantage in the machining of micro slots/grooves in titanium alloys.However,when the machining of titanium alloys using aqueous base electrolyte,the destruction and formation of the passive film will occur repeatedly on the surface of the titanium alloys,which will lead to the difficulty of electrochemical machining.The controllability of machining will be reduced when the machining parameters are enlarged.In this paper,ethylene glycol solution is utilized as electrolyte to machine titanium alloys.Due to the low proportion of water molecule in ethylene glycol solution,the passive phenomenon can be reduced and therefore the machinability of titanium alloys are improved in electrochemical machining.The main research contents are listed as follows:(1)The dissolution mechanism of titanium alloys in aqueous base solution and ethylene glycol base solution was analyzed.It was found that ethylene glycol solution can help to reduce passivation in electrochemical machining process and improve the machinability of titanium alloys.(2)The polarization curves of pure titanium and Ti6Al4 V in different electrolytes were measured and analyzed.It was found obvious passive and transpassive region exists in aqueous base solution,while there is no obvious passive and transpassive region in ethylene glycol base solution.(3)An experiment system for electrochemical machining micro-slits was set up.Experiments were carried to investigate electrochemical micromachining micro-slits in titanium alloys using helical electrode.Results show that NaCl-ethylene glycol solution is suitable for machining titanium alloys.With the use of optimal machining parameters,micro-structures with high precision were fabricated.(4)An experiment system for electrochemical machining micro-grooves was set up.The electric field simulation when electrochemical machining using the dentate disk electrodes was carried out.Experiments were carried out to investigate electrochemical micromachining micro-grooves in titanium alloy using self-designed dentate disk electrode.Results show that micro groove with small taper was successfully machined by optimal machining parameters,including optimal dentate disk electrode,electrode insulation,and low voltage.