| Electrochemical machining(ECM)has high processing efficiency,can obtain non-damaged machining surfaces.Therefore,it has unique advantages for the processing of complex structural parts for TiAl alloy and other difficult-to-machine materials,and is widely used in aerospace,defense,automotive and medical applications.However,the electrochemical machining process is influenced by the interaction of multi-physical fields such as electric field,electrochemical field,thermal field,flow field,etc,which makes that the machining accuracy,surface quality,and the stability of the machining process are difficult to control.In order to obtain a better machining process,a large amount of experimental research is required,which greatly increases the cost of process development and extends the development cycle.In this paper,the evolution and the influencing mechanism during the electrochemical machining process of the macro-state parameters and the micro-morphology of the machined surface were carried out by the computer simulation research,which is helpful for the optimization of design process parameters.The results can provide a theoretical guidance for the electrochemical machining experiment and are of great significance for improving the quality of the machined surface.The macro phenomena of electrochemical machining process,such as the distribution and evolution of the machining gap,the current density,the temperature and the bubble rate were investigated,and therefore,the evolution and the influencing factors of the surface morphology in the machining process were analyzed to reveal the forming mechanism of the machined surface.The main research contents and results are as follows:(1)The electrochemical corrosion behavior of two-phase Ti-48Al-2Cr-2Nb alloy,single-phase y-TiAl alloy and single-phase?2-Ti3Al alloy was analyzed by electrochemical impedance spectroscopy,and the dynamic parameters of the three types of alloys were obtained.The results show that single-phase ?2-Ti3Al alloy has stronger corrosion resistance than single-phase y-TiAl alloy and has a similar corrosion behavior compared to the two-phase Ti-48Al-2Cr-2Nb.(2)A gas-liquid two-phase flow multi-field coupling macro model of the electrochemical machining of Ti-48Al-2Cr-2Nb alloy on the COMSOL Multiphysics simulation platform was established,and analyze the process parameters such as voltage,solution flow rate,feed rate,etc Influence on temperature,current density,processing gap,bubble rate and other distributions.The results show that during the DC electrochemical machining process,the current density and machining gap were significantly influenced by the flow rate of electrolyte and the feed rate,the current density distribution is more uniform with their increase.But when the electrode feed rate is 2.3mm/min,the local current density has a sharp increase,which is resulted from the higher feed rate making the smaller machining gap and preventing the excretion of corrosion products and bubbles.In the pulse electrochemical machining process,the pulse frequency has a significant effect on the bubbles and temperature in the process.When the pulse frequency reaches to 3kHz,the waveform fluctuation amplitude of temperature and bubble rate is less than 1? and 2%,respectively.(3)The position function was used to establish the micro-material model for two-phase Ti-48Al-2Cr-2Nb alloy,and then the electrochemical machining simulation micro-physical model was set up.The influences of the macro-process parameters and the microstructure of alloys on the evolution behavior of surface micro-morphology were investigated.The results show that when the flow rate and feed rate is in the range of 14.7m/s-23.4m/s and 1.7mm/min-2.1mm/min,respectively,the roughness Ry of the machined surface decrease with their increase.The smoothest surface(Ry 0.7?m)is obtained under the condition of the voltage 21V,the feed rate 2.1mm/min,the electrolyte flow rate 23.4m/s.In addition,the machined surface becomes smoother with the increase of the angle with the feed direction of lamellar structure of alloys. |
PDF Full Text Request