Fundamental Research On Micro-Milling Technology Of High Volume Fraction Silicon Carbide Aluminum Matrix Composites

SiC particles reinforced aluminum matrix composites(SiCp/Al)have the advantages of high specific strength,specific modulus,high temperature resistance and wear resistance.However,the different properties of SiCp/Al composites in matrix phase and reinforcement phase make their machining mechanism complex and surface defects serious,which seriously affect the application of this material in precision field.In order to improve the micro-milling process of SiCp/Al composites,In this paper,the removal mechanism,surface morphology and defect formation mechanism of SiCp/Al composites are studied by combining finite element simulation technology and experiment.In the milling process of SiCp/2024Al composites,the interaction between cutter,particle and matrix is extremely complex.It is difficult to determine the milling mechanism and surface defect formation process of the composites through experiments.In order to study the removal mechanism and surface defects of SiCp/2024Al composite,a multi-particle microscopic finite element simulation model was established,analyzing the distribution of stress and strain,the cutting mechanism of different tool-particle contact position and the blunt circular radius of different cutting blades,and the influence of cutting speed and feed per tooth on the surface quality of the material.Firstly,the cutting mechanism of SiCp/2024Al composite,the microscopic morphology of the cutting parameters,the surface roughness and the influence of the feed per tooth on the subsurface damage depth of the processed material were studied.The results show that from the microscopic point of view,when the tool cuts the upper part of the particle,the particle is broken off,and with the increase of cutting speed,the breaking degree is weakened,and the surface defects are mainly cracks.When the tool cuts the lower part of the particle,the particle is mainly removed,and the surface defect is a large pit.Appropriately increasing the spindle speed can improve the surface quality of the machined workpiece.The increase of the feed rate of each tooth will lead to the increase of the surface defect of the machined workpiece and the deterioration of the surface quality.With the increase of feed rate per tooth,the thickness of the subsurface damage layer of the workpiece increases,the defects on the side of the milling groove increase,and the damage depth of cracks and pits increases.The cutting depth has the greatest effect on surface roughness,the spindle speed is the second,and the feed rate has the least effect.Secondly,a comprehensive study is made on the above content from the mesoscopic size point of view.The results show that because the radius of the blunt circle of the cutting edge is very large relative to the particle,the particle removal is mainly broken.The increase of spindle speed and feed per tooth will lead to the increase of material surface defects and the deterioration of surface quality.With the increase of milling depth,the surface quality of material becomes better.With the increase of feed rate,the thickness of subsurface damage layer will increase,and the crack and pit will become deeper.The feed rate has the greatest influence on the surface roughness,followed by the spindle speed and the cutting depth has the least influence.Finally,the effect of the radius of the blunt cutting edge on the cutting mechanism was studied.The results show that when milling SiCp/2024Al composite materials with small cutting blade,the main removal form is extraction,crushing and pressing,most of the resulting chips are semi-continuous zigzag chips,less with small spiral chips,less processed surface defects,less defect damage,more likely to produce good quality surface appearance.The main removal form of particles when milling SiCp/2024Al composite is separation,extrusion,crushing and rolling,most of the chips are small spiral chips and a few have semi-continuous zigzag chips.The former has better processed surface quality and fewer defects than the later,and has less Von Mises stress during cutting.