Study On Pulsed Laser Ablation Of Silicon Carbide Particulate Reinforced Aluminum Matrix Composite

Silicon carbide particulate reinforced aluminum metal matrix composite（SiC_p/Al）is one of the most promising aviation key materils,but its industrialization is restricted by its processing technique owing to the serious wear and tear of the processing tool,low efficiency of processing,rough surface after processing,and the limitation in processing shape.As an advanced processing technique,pulsed laser has the advantage in material processing because of its flexibility and adaptability.Comparing with continuous laser,pulsed laser shortens the time of laser material interaction,reduces the heat influence,improves the machining precision,and showes good application prospects in micro/nano-processing.What’s more,pulsed laser is becoming more mature in processing of metal,ceramic,semiconductor and other materials.At present,the processing of composite materials by pulsed laser is mainly focused on the research and application of cutting and drilling.However,pulsed laser processing of ceramic particle reinforced metal matrix composites is rarely reported.Because of the many problems existing in the traditional processing methhods for SiC_p/Al composite and the characteristics and advantages of the pulse laser ablation,in this parper,a study using pulsed laser ablation SiC_p/Al composite is carried out in this paper.The main contents include:firstly,the general rules of interaction behaviors are obtained by using nanosecond single pulse irradiating on SiC_p/Al composite;the interaction between matrix and reforcement are obtained by comparison experiments between composite materials and single bulk.On the basis of this research,study on scanning ablation technology of SiC_p/Al composite is carried out.The plasma’s effect on ablation is experimentally tested,and a“jump ablation”method is presented and the processing technology is optimized.In the end,this paper makes a preliminary study on ultrashort pulsed laser ablation of SiC_p/Al composite.Two-temerature modeling of Al and SiC materials is carried out to obtain the characteristics of ultrashort pulse laser ablation of SiCp/Al composite and the formation mechanism of surface morphology.By summaring the characteristics of this processing,the shortcomings and defects are analyzed and forecasted.The following conclusions are made.Firstly,nanosecond single pulse is used irradiating on AA2024 block,SiC block,and SiC_p/AA2024 composites with 5μm and 30μm average particle diameters.Results show that nanosecond laser affecting range on composite is larger than the bulk material,the larger particles the range is larger.The composite matrix etching depth is less than the bulk AA2024,and the matrix’etching depth is larger for large particles reinforced composite.The ablation behavior is similar to bulk for small particle reinforced composite.Thermal modeling and reflectivity measurement of AA2024 and SiC shows that SiC heats up faster than AA2024 and has higher absorption rate.Therefore,SiC particle acts as a high absorptive and rapid heating material randomly and discretely distributing in composite that can improve the composite absorption rate,expand the pulse affecting range,accelerate the matrix melting,reduce the matrix damage threshold and improve its ablation rate.The larger SiC particle,the more obvious the interaction between particle and matrix.Secondly,study on processing technology shows that:The plasma’s absorption of secondary pulse’s energy is the main reason reducing the laser energy utilization.Therefore,ablation depth increased in logarithm and showed saturation trend with increasing beam overlap.The defect accumulation effect is the main way enhancing the material absorption rate.Therefore,ablation dpeht and surface roughness increased linearly with increasing ablating passes.By combining nanosecond laser’s inducing large numbers of melten pool,high pressure coaxial gas mechanically assists ablation,improving the ablation rate and reducing both the resolidification thickness and roughness.Therefore,ablation depth and ablation rate increased linearly and both the surface roughness and re-solidification thickness saturated with increasing pulse energy.In order to minize the plasma’s affect on abltion,a“jump ablation”method is presented.Compared with the ablation result with plasma affect,ablation depth increases significantly.Due to the thermal effect of nanosecond laser,the surface of the SiC_p/AA2024 composite after ablation has metallurgical reaction.The resolidification layer composes of mainly Al₉Si,SiC,and a small amout of SiO₂,Si,Al₄C₃,and Al₄SiC₄ products.The chemical components’distribution is relatively uniform.Finally,experiment results of picosecond laser ablation of SiC_p/AA6061show that,the morphology and ablation law are different from those of nanosecond laser ablation.Because the picosecond lase can ablate the matrix and particle directly in gaseous form,ablation surface shows no resolification.The ablation depth and surface roughness increase linearly with pulse fluence,and the ablation’s depth after 100scanning passes is two times of 50 scanning passes.The two-temperature modeling result shows that the matrix vaporizes faster than silicon carbide,a surface morphology of deeper etching of matrix and SiC particle emerging was formed.Besides,the characteris of the ablation morphology was enhanced with the increasing of ablation passes and fluence,and therefore the surface roughness was increased.