Study On The Laser-assisted Micro Machining Of Metal Matrix Composites

Compared with conventional material,the metal matrix composites have higher specific strength and modulus of elasticity,good dimensional stability,high temperature stability,and so on.It has been widely used in the field of aerospace,aviation and military and in the civil field as well,such as automobile manufacturing.Particle reinforced metal matrix composites have significant advantages in cost over other types of reinforcements,because they have better isotropy and have higher material performance than other types.Therefore,the particle reinforced metal matrix composites have a more promising market in engineering applications.But because the high hardness materials of the particles,unable to use traditional machining method to obtain good processing quality,there will be reinforcements fracture,reinforcements and matrix interface rupture and reinforcement detached phenomenon,and with the increasement of particle volume percentage,tool wear and cutting energy consumption will increase.The surface quality of metal matrix composites is improved by EDM,but there are two times of discharge during machining,which will cause the radial cutting of materials easily.While increasing the processing current,the removal rate can be raised,but the wear of the electrode is increased as well.Though the EDM efficiency can be increased with the improvement of discharge parameters and the scouring efficiency,the efficiency is still obviously less than that of traditional machining methods.The industrial application has a high requirement for the removal rate of materials.Therefore,a processing method with high efficiency and good processing quality for the particle reinforced metal matrix composites should be studied.Laser assisted machining process is a new machining method to solve the low efficiency of machining of difficult processing materials,which is through the interaction between the laser and the material and changes its mechanical performance before the material be removed.But the laser assisted cutting technology in general be researched in macro scale.Micro cutting is rarely reported.With the continuous development of aerospace,defense industry and microelectronics industry,small precision 3D complex structure component has become increasingly urgent.Micro thin walled cavity surface,complex shaped,integrated structure made by metal matrix composites are utilized to ensure high safety and reliability of the system under high overload,high speed,high rotation and other harsh environment.Although metal matrix composites possess good performance of micro structure,the difficulty of machining is increased as well.In this paper,the laser assisted micro machining of particle reinforced metal matrix composites is studied.Through the combination of precision micro cutting experiment and numerical simulation,the form mechanism and evolution rule of micro flaw on the surface layer of particle reinforced metal matrix composites during laser assisted micro machining process are analyzed,and the essential characteristics of laser assisted micro cutting process of metal matrix composites are further revealed.The key research points including the following aspects:(1)The micro cutting experiment and simulation of metal matrix composites machiningAiming at SiCp/2024 Al composites,by constructing material constitutive relationship,ABAQUS/Explicit micro analysis software was applied to simulate micro cutting process with the establishment of composites constitutive relationship,and the influence rule of reinforced particles on micro cutting performance of SiCp/2024 Al composites was studied.The results of micro cutting simulation are compared with the results of real cutting experiment under the same parameters,and the finite element simulation method is modified and perfected,which lays the basics for the research of the process characteristics of laser assisted micro machining SiCp/2024 Al composites.(2)The effect of laser parameters on the friction properties and wear performance of SiCp/2024 Al compositesTemperature field of laser heating of SiCp/2024 Al composites is researched.The relationship between thermal conductivity and particle volume percentage is analyzed.Temperature variation with different laser power and velocity were calculated based on the analysis of material properties.Influence analysis of temperature on the material friction performance is studied by friction and wear test which laid the foundation for the study on the influence of laser and cutting parameters on machining quality and tool wear.(3)The influence of laser assisted micro cutting parameters on the formation of surface microcosmic defectsA model for the micro cutting stress field is established.Combined with the influence of temperature field on material friction and fracture mechanics performance,the influence of different laser power and cutting parameters on cutting force is analyzed.A series of laser assisted micro cutting experiments for SiCp/2024 Al composites are carried out.The orthogonal experiment results are analyzed with ANOVA accordingly.The cutting depth,cutting speed and laser power are found to have significance effect on the cutting force,and laser power has the largest effect among those factors;cutting speed is contribute to the improvement of the surface roughness,but when a too high cutting speed is used,it will accelerate tool wear on the surface and the decline in the quality.The cutting depth should be slightly larger than the average particle size range.Reasonable laser power can reduce the roughness of about 14%.The surface integrity after laser assisted micromachining has been greatly improved.In the laser assisted micro machining,the mechanical wear and chemical wear are found both taken place in the cutting tool,and the wear forms are mainly abrasive wear and adhesion wear.The cutting thickness and laser power have a significant effect on the tool wear.The volume of tool wear is decreased with the increase of laser power.When the laser power increases from 0W to 27 W,there is a reduction of flank wear by 38%.To observe and analyze the formation of chip laser assisted micro cutting process,a high-speed video camera is utilized and the microstructure of machined surface layer is observed by scanning electron microscopy,investigation of deformation and evolution characteristics of micro structure of the material surface layer under different laser energy and micro cutting parameters are conducted.The surface damage during laser assisted micro cutting process is analyzed.On these basics,the X ray energy spectrum analyzer is used to analyze the change of elements in the process,and the existence of Al2O3 nanoparticles in the process is verified.The reasons for the improvement of surface integrity in the process of laser assisted micromachining are explained in terms of the friction effect and filling effect caused by the nanoparticles.