Research On Machining Technology And Surface Integrity Of Ultrasonic Milling Of Titanium-aluminum Alloys

TiAl alloy is more and more widely used in low-pressure turbine aero-engine.However,as a typical refractory metal,it is difficult to achieve high-quality machining of titanium aluminum alloy by using traditional processing methods and cutting techniques.In this paper,a systematic study on ultrasonic milling of titanium alloy was carried out by combining experimental research and theoretical analysis from the aspects of tool wear,surface integrity,milling force and parameter optimization.The effects of milling parameters and cutting distance on tool life and wear during ultrasonic assisted milling of TiAl alloy were studied by orthogonal test and single factor test,the results show that the influence of milling parameters on the tool life,with the increase of cutting length,tool wear status showed evident in three stages.The back surface of the tool is mainly bonded wear,supplemented by oxidation wear and diffusion wear,while the front surface is mainly diffusion wear and bonding wear,supplemented by oxidation wear,accompanied by coating peeling.Ultrasonic vibration can effectively delay the appearance of material binding,oxidation wear and other phenomena.The influence of cutting parameters on the surface quality and microhardness of the surface layer in ultrasonic milling was studied by single factor experiment,draw the conclusion: the processing surface quality with the increase of milling speed variation before they get better,with the increase of each z feed and cutting depth and variation,end milling,ultrasonic current would increase than the surface texture characteristics,surface tends to be isotropic,roughness increases;In the side milling state,the z-axis vibration has little change on the surface morphology,and the surface texture characteristic ratio has little change.The surface roughness reduced Compared with no ultrasonic machining.Based on the analysis of the trajectory of the tip and the relative position of the cutterworkpiece,it is concluded that the difference of the milling force between the axial ultrasonic machining and traditional machining is mainly caused by the change of the instantaneous relative velocity of the cutter-workpiece,rather than the change of the chip thickness and length.The influence of milling parameters on milling force was studied by single factor test,and it was found that the influence of milling parameters on milling force was regular in both end milling and side milling,and the introduction of ultrasonic could effectively reduce the milling force within a certain range.The parameter optimization of TiAl alloy in ultrasonic milling was studied.According to the characteristics of long tool life but reduced surface roughness during ultrasonic milling,a double-objective optimization model of TiAl alloy rough machining was established with tool life and milling efficiency as the targets.According to the characteristics that ultrasonic side milling can reduce the surface roughness and milling force,a three-objective optimization model was established,with surface roughness and milling force as the main objectives and milling efficiency as the secondary objectives,and the basis of cutting parameters was given for different objective function combinations.