Micro-surface Formation Mechanism And Experimental Study In Ultra-precision Cutting Of ¹⁰B/Al Composite

¹⁰B/Al composite is an excellent simulation material about helium damage,which has been gradually applied in the field of nuclear technology.With the development of high-performance computing capabilities,high confidence experiments for helium damage simulations have placed significant demands on the high surface integrity of¹⁰B/Al composite samples.Diamond cutting is an effective method to achieve high surface integrity processing.However,¹⁰B/Al composite material as a special aluminum matrix composite material,its reinforcing phase?boron particles?has has characters of high hardness,low content,uneven distribution,so the cutting process is prone to brittle failure,which seriously affects the surface integrity.The micro-formation of ¹⁰B/Al composites is closely related to the failure modes of boron particles.The failure mode is closely related to the microstructure,static/dynamic mechanical properties and cutting conditions of the material itself.By studying the microstructure and mechanical properties of the material,both cutting characteristics and formation mechanism of the cutting surface are acquired.Moreover,the influence of cutting conditions on surface formation was studied,which has great contribution to ptimize process.Firstly,by multi-channel analysis and testing methods,the micro-structure of the material was recognized and the composition of the reinforce phase was determined.Then the effects of reinforce phase on the relative tensile properties and interfacial properties were determined by testing the tensile properties and nanoindentation microhardness.Based on the micro-structure and static mechanical properties,the dynamic mechanical properties of ¹⁰B/Al composites and high purity aluminium materials at different strain rates and temperatures were tested by the high temperature separated Hopkinson pressure bar experimental device.The stress-strain curves under various impact loads were obtained.Therefore,the flow characteristics and dynamic interface characteristics of the ¹⁰B/Al composites material were understood.Based on the measured experimental data of high purity aluminium and ¹⁰B/Al composites,two constitutive models,Power-Law and Johnson-Cook,were used to fit the model,and the fitting errors of the two models were compared and analyzed.The conclusion shows that Johnson-Cook constitutive model has higher fitting accuracy and is more suitable for subsequent simulation.According to the microstructure and static/dynamic mechanical properties of the material,the cutting characteristics based on the hardness and brittleness of the reinforce phase and its high interfacial adhesion with the substrate were studied,a mapping model from the stress status of boron particles to the failure mode,and then to the surface morphology was established.The influence of the stress state of boron particles on the failure mode was studied,and the formation mechanism of cutting micro-surface under different failure modes was studied,focusing on the mechanism of crack generation and expansion when boron particles are pressed;The finite element modeling and simulation of relative cutting thickness?ratio of cutting thickness to boron particle size?and cutting speed were carried out.The influential mechanism of cutting thickness and cutting speed on the micro-surface formation was studied,at the same time the probability model of surface quality was established,and the statistical results are fitted with Gauss function according to the model.The simulation results are in good agreement with the statistical results.In order to validate the established cutting model,an orthogonal experiment of four factors and three levels,which includes the cooling and lubrication conditions,cutting depth,rotating speed and feed,it was designed in combination with on-line and in-situ observation of cutting process.On one hand,the model and simulation results were verified.On the other hand,the influence of cutting conditions,boron content and other factors on the surface quality was studied by experiments,and the process optimization scheme was determined.Then the validity of the cutting mechanism and simulation model was verified by the experimental results.On-line observation of the cutting process of the optimized process scheme by high-speed photography revealed that the plastic continuous cutting can be formed by using the optimized process parameters,and the surface damage can be minimal,which is a good proof of the process optimization scheme.The above research shows that the fracture mode of boron particles has an important influence on the cutting surface formation.By optimizing the cutting conditions,the breakage of boron particles can be reduced,and continuous cutting can be formed on boron particle and the interface between boron particles with matrix.Such model can help to get the integrity surface and achieve high-quality manufacturing of high-performance numerical simulation experimental samples.