Research On Micro Milling Mechanisms And Machinability Enhancement Process Of SiCp/Al Composites

Precision manufacturing with high-performance composite materials has become an important direction for the development of advanced equipment in the fields of aerospace and defence and others.In the micro milling process of SiCp/Al composites,the microstructure can’t be ignored due to the small cutting scale,the contact beween tool and reinforcement/matrix/interface are complicated,and the damage mode of reinforced particles in the cutting deformation zone is difficult to determine.The metioned above have brought great chanllenges to the accurate modelling of cutting forces and tool wear in the micro milling of SiCp/Al composites.Besides,the presence of high-hardness ceramic particles in the cutting area makes the machinability of the material poor,so there is a need to explore new method to solve the problems of excessive tool wear and poor surface integrity caused by the reinforced particles in the processing of SiCp/Al composites.Therefore,it is of great significance to propose the accurate predictive model of cutting force,tool wear considering the microstructure and size effects as well as a new processing method that combines laser surface heating and precision milling.This paper focuses on the micro milling mechanism and machinability enhancement process of SiCp/Al composites.The main contents are as follows:An analytical model of cutting forces in the micro milling of SiCp/Al composites considering interface failure was estabilised.A new algorithm was proposed to estimate the particles debonding force caused by interface failure with the aid of Nardin-Schultz model.An improved Weibull model was applied to estimate the precent of particle cracking and debonding in the cutting of SiCp/Al composites.An algorithm model for the sliding friction coefficient of the rake face was proposed considering the two-body abrasion and three-body rolling of reinforced particles.Several aspects of the cutting forces generation mechanism are considered including particles debonding forces in the shear zone and build-up region,particles cracking forces in the build-up region,shearing and ploughing forces of the metal matrix.The accurate prediction of the cutting force in the micro milling of ceramic particles reinforced metal matrix composites was achieved.The effects of interface failure,reinforced particles and edge radius on the micro milling process were analyzed.The flank wear progression and mechanism of PCD micro end-mill during the micro milling of SiCp/Al composites were revealed.The tool flank wear land width model was developed incorporating the two-body abrasive wear,the three-body abrasive wear and the adhesive wear.The composite material wear characteristics,the probability distribution of reinforced particles sizes,the reinforced particles conglomeration and the size effects of micro-scale machining are taken into account in this model.Finally,the effects of different wear mechanisms,reinforced particles,machining conditions and tool parameters on the tool flank wear progressions were analyzed.In order to improve the problems of high cutting resistance,rapid tool wear and unsatisfactory surface integrity during the machining process of SiCp/Al composites,a material processing method combining laser surface heating processing and precision milling was presented.The effects of laser processing parameters and reinforcement volume fraction on the laser acting zone were studied.The finite element model of laser heating temperature field for SiCp/Al composites was established,and the microstructure forming mechanism of the laser acting zone under the optimal parameters were revealed by using the temperature field model.The original experimental workshop and precision milling experimental platform were upgraded to meet the precision milling requirements of SiCp/Al composites.The differences between the laser acting zone and the original zone in cutting forces,tool wear and so on were compared and analyzed,and the mechanisms of improving the machinability of laser acted SiCp/Al composites were revealed.On these bases,the proposed processing method was validated with 20vol% SiCp/2a14 Al composite and 40vol% SiCp/Al composite.