Research On Laser-milling Process And Residual Stress Of Particle Reinforced Aluminum Matrix Composites

SiC particle reinforced aluminum matrix composite(SiCp/Al)has shown great application prospects in aerospace,high-end equipment,automotive electronics and other fields due to its excellent comprehensive characteristics of high specific stiffness,high specific strength,high temperature resistance,wear resistance and dimensional stability.SiCp/Al composites are faced with many problems in machining,such as serious tool wear,poor machining accuracy and surface integrity.In this paper,the milling surface integrity and residual stress were studied through numerical simulation and experimental method,simulating the milling temperature and residual stress.Furthermore,laser-CNC milling cooperative processing technique is proposed to improve the machining efficiency and realizes the excellent distribution of surface residual stress,providing a theoretical and experimental basis for expanding the application of aluminum matrix composites.The major achievements are as follows:1.The orthogonal cutting simulation model of SiCp/Al composites was developed to simulate the cutting process.And combined with the full factor milling test to characterize the milling surface integrity and residual stress of SiCp/Al composite,exploring the effect of parameters on material removal mechanism,milling force,surface defects,residual stress distribution and burr.It was found that the different relative position between the reinforced particles and cutting path of the tool edge lead to different particle removal modes such as fracture,shear and pull out,resulting in different surface defects such as pits,cavities and scratches.The cutting force,surface roughness and the thickness of subsurface damage layer increased as the cutting speed and feed rate increased.The machined surface and shallow sub-surface show residual compressive stress.2.A three-dimensional milling temperature simulation model of SiCp/Al composites is built.Meanwhile,milling experiments of SiCp/Al composites are carried out to investigate the impact of milling process parameters on surface quality and milling temperature.The results showed that the model could effectively realizes the simulation of milling temperature.And the milling temperature will be higher when increased milling speed and feed rate per tooth under the combined action of elasticplastic deformation heat generation and friction heat generation of materials.Thus deeper feed marks and more surface defects such as cavities and holes were formed due to the fact that SiC reinforced particles were easier to be pulled out,resulting in higher surface roughness.3.High power laser-CNC milling cooperative machining process of SiCp/Al composites was proposed.Through experiments,the advantages of the new processing technology are analyzed,and revealed the correspondence between process parameters and the machined surface quality,as well as residual stress,so as to optimize the processing parameters.Results showed that the cooperative processing not only makes up for the defect of poor surface quality of laser cutting,but also improved the residual stress of machined surface through stress superposition and reorganization,and finally formed the surface residual compressive stress which is conducive to improving the fatigue life and service performance of parts.The surface residual compressive stress after collaborative machining increases slightly with the increase of axial milling depth but decreases as milling speed increased.The heat affected zone size of laser cutting could be deduced from the sub-surface microstructure,which provides a basis for the optimization of process parameters.