Study On Chip Curling And Chip Morphology Of Ti-5553 Titanium Alloy Under Different Cooling Strategies

As a new generation of aviationn material,titanium alloy Ti-5553 has the advantages of low segregation sensitivity,good hardenability,high specific strength and fracture toughness.But the mechanical property machinability of ti-5553 is poor.Chips are not easy to break and winding chip s are often produced with high cutting area temperature during processing which make the surface quality of the workpiece and tool wear become poor and violent.Traditional processing methods cannot meet its processing requirements and there are few studies on Ti-5553 chip morphology at present.Therefore,in this paper,high pressure cooling and liquid nitrogen cryogenic cooling assisted cutting methods,the chip curling and chip morphology of titanium alloy Ti-5553 under different cooling strategies are studied to provide theoretical and experimental basis for the cutting mechanism of Ti-5553 with high efficiency.The specific research contents are as follows:The force of the chip under high pressure cooling conditions is studied at first by solving the chip combined force and moment and analyzing the chip stress distribution and force balance under high pressure;The chip curl radius model under high pressure is established based on the curl radius result from the velocity vector diagram;Then,by limiting the nozzle diameter to control the liquid nitrogen injection flow rate,combined with cutting parameters and experimental results,an experimental model of cryogenic curl radius of liquid nitrogen was established;Finally,the chip breaking mechanism under two cooling strategies is analyzed,and the chip breaking criterion is proposed based on the maximum strain theory.The theoretical model of chip crimp radius under high pressure is verified by high variable pressure turning experiments.The orthogonal experiment of four factors and three levels was carried out for liquid nitrogen cryogenic cutting.In order to investigate the difference of chip morphology under three cooling methods,a comparative turning experiment was designed under these three methods.Chip samples were collected for subsequent comparative analysis,and using comparative test data to further verify the model of chip curl radius under high pressure and cryogenic.The macroscopic morphology of titanium alloy Ti-5553 chips under three cutting methods is analyzed,and the types of chips generated under several cooling methods are compared.The macroscopic morphology of chips under three cooling strategies includes: chip curl radius,chip pitch,and chip thickness and the chip breaking length.Furthermore,the influence of different cooling strategies on the macro morphology of chips was obtained.In order to analyze the microstructure of Ti-5553 chip under different cooling strategies,Keyence VHX-1000 ultra-depth of field 3D microscope,scanning electron microscope and metalloscope were used to measure and observe.Micromorphology includes chip free surface,back surface,serrated cross section(including adiabatic shear band)and fracture surface.Analyzing the reason for differences from phenomenon to essence.Finally,the optimal cutting parameters under the cutting condition of Ti-5553 were obtained by combining the macro chip morphology and fracture condition.