| Silicon carbide particle reinforced aluminum matrix composite(SiCp/Al)has the characteristics of light weight,high temperature resistance,high modulus,excellent wear resistance and so on,which has been widely used in automotive,electronic products and aerospace fields.As a non-contact,nonabrasive processing method,laser cutting has the advantages of energy concentration,high efficiency,low cost,no cutting force,automation and so on.It is an ideal choice for cutting SiCp/Al composites.The difference of thermal properties between matrix material and reinforcement leads to various damages in laser processing,which seriously affects the quality and service performance of composite parts.In view of various thermal damage problems formed in the process of laser cutting SiCp/Al composite materials,the formation mechanism of thermal damage in the process of high-power fiber laser processing of composite materials with different SiC particle volume fraction was studied,and the influence of process parameters on the processing quality was established by finite element simulation model.The temperature field and stress field distribution in laser cutting SiCp/Al composite were analyzed.The main research contents and conclusions are as follows:(1)The feasibility study of high-efficiency cutting of high-volume fraction(65%)SiCp/Al composites with different thicknesses by CW fiber laser was carried out.The influence of laser process parameters on kerf characteristics and surface morphology was analyzed,and the formation mechanism of kerf characteristics was clarified.The results show that the thermal damage of high-volume fraction SiCp/Al composites in laser cutting is mainly caused by the difference of thermal properties between aluminum alloy matrix and SiC particles.The SiC particle reinforcement with high thermal conductivity caused the heat to diverge,and reduced the material removal rate.The heat stored by the high viscosity molten composite further damages the kerf quality.(2)The relationship between process parameters and surface quality during laser cutting of low-volume fraction(20%)SiCp/Al composites was studied systematically.The effects of laser power,cutting speed and assist gas type on surface morphology and defect characteristics were studied;The kerf characteristics and machining surface defects were quantitatively analyzed,and a quantitative measurement method of dross adhesion degree was established;The morphology characteristics and HAZ distribution of different positions on the cross section were analyzed by scanning electron microscopy(SEM)and electron energy spectrum(EDX).The significant influence of laser process parameters on machining quality and the mechanism of damage formation were revealed.The results provide theoretical basis laser processing of low volume fraction SiCp/Al composites.(2)The effects of laser cutting process parameters on the surface quality of 20%SiCp/Al composites were studied,and the effects of laser power,cutting speed and assist gas type on the surface morphology and thermal damage defect characteristics were analyzed.The kerf characteristics and the distribution of surface defects were quantitatively characterized,the measurement method of the degree of dross and adhesion on the machined surface was proposed.The morphological characteristics of different locations and the distribution of heat affected zone were analyzed.The experiment results showed that the material removal rate was significantly higher in laser cutting of 20%SiCp/Al composites,the kerf feature quantization was more accurate and the machined surface flatness was batter.Thermal defects were highly associate with cutting parameters,and typical defects including cataphracted dross,droplet dross,protuberances,microcracks,and combustion.There are cracks and other defects on the sub-surface,while the thermal damage is in a controllable range.(3)The influence of laser processing parameters on kerf geometry was studied by statistical analysis method,and the ideal cutting speed,laser power and assist gas pressure were determined.The removal mechanism of SiCp/Al composites by laser processing was elucidated.A three-dimensional finite element model of laser cutting SiCp/Al composites was established,and the influence of laser process parameters on temperature field distribution was analyzed,the removal model of composites was further improved according to temperature field distribution.The distribution of residual stress in laser cutting composites was analyzed and compared with the experimental records.It provides a theoretical basis for related experiments and simplification of composite model. |
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