| Deeply grasping the cutting mechanism is the basis of improving the processing efficiency and quality.At present,domestic and foreign scholars are still in the initial stage of research on the cutting mechanism of titanium and aluminium alloys,and lack of systematic and in-depth research.In this paper,the cutting mechanism of ?-TiAl alloy is systematically studied by combining theoretical analysis with cutting experiment.It can provide theoretical basis for the optimization of technological parameters,the guarantee of processing quality and the extension of tool life in the cutting process of ?-TiAl alloy.The influence of cutting parameters on tool life,surface quality and cutting force have been studied,and the roughly range of cutting parameters for turning ?-TiAl alloy was determined.Considering the tool life,quality and efficiency,the optimum cutting parameters range of rough and semi-finish machining for cutting speed of 50m/min,feed rate of less than0.1mm/r,depth of cut of 0.2-0.3mm.The optimum cutting parameters range of finish machining for cutting speed of 50m/min,depth of cut of 0.2mm,feed rate of 0.02mm/r.The failure modes and mechanisms of YG8 cemented carbide tool were studied.The results show that YG8 cemented carbide tool turning ?-TiAl alloy has two main failure modes:wear and breakage.Tool wear is mainly bond wear,while there will be a certain degree of diffusion wear and oxidation wear.Oxidation wear and diffusion wear will increase by the increasing of cutting parameters,then resulting in tool life reduction.Excessive cutting parameters will lead to tool breakage in a very short time.At the same time,tool wear will also lead to tool breakage after stable cutting for a period of time.Chip formation and surface quality of ?-TiAl alloy were studied.Chips and machined surfaces were observed,the results show that there are obvious slip phenomena at the free end of the chip.At the same time,with the decrease of depth of cut and feed rate,the chip transits from fragmented chip to near-banded chip,and then evolves into banded chip.When the banded chip is formed,the surface without pits and cracks is obtained.Based on the mechanical properties and micro-structure of the alloy,the chip formation model was established,and the chip formation mechanism was preliminarily revealed.The relationship between chip morphology and the machined surface morphology of the workpiece was also discussed.The influence of the VB,cutting speed,depth of cut and feed rate on the cutting force have been studied.It is found that the cutting force is approximately linear with depth of cutand feed rate.The cutting speed has little effect on the cutting force.With the increase of the VB,the cutting force will increase significantly.Considering the influence of tool flank wear on cutting force,a model of turning force of ?-TiAl alloy based on tool wear was established.The model coefficients were determined by experiments.Finally,the model of turning force was validated and analyzed.The results show that the relative errors of the experimental and predicted values are less than 20%,and most of the relative errors are less than 12%.The model can better reflect the change of cutting force. |
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