Effect Of Different Quality SiC Particles On Fabrication And Mechanical Property Of Aluminum Matrix Composite With High Volume Fraction

High volume fraction(HVF)SiCp/Al composites were prepared by pressureless infiltration using original and ultrasonic cleaned,domestic abrasive grade,green SiC particles.The effect of the different quality SiC particles on the infiltration process and mechanical property of the SiCp/Al composite was studied by laboratory experiments and by means of scanning electron microscopy,X-ray diffraction technique and three-point bend test,aiming to improve the adaptability of the domestic abrasive grade SiC particles to the pressureless infiltration process of the HVF SiCp/Al composites.The results of particle characterization and ultrasonic cleaning experiment show that all of the studied SiC particles(No.1?No.8)are adhered by the adsorbate with varying mass fraction(0.08%-0.58%).The adsorbates are mainly fine SiC particles(diameter less than)and,in certain cases,low fraction of carbon and silicon dioxide.Most kinds of the SiC particles present a polygonal morphology,with few products presenting sharp edges.The adsorbate could be cleaned effectively by ultrasonic cleaning method using deionized water medium,which is not very effective for the particles with low mass fraction of the adsorbate.In comparison,the cleaning efficiency could be improved in alcohol medium,although the cleaning results are the same.The infiltrating experiments indicate that,for all of the original particles(No.1?No.8),only No.6 and No.8 particles could be successfully used to prepare the SiCp/Al composites,with the success rate being only 25%.This is because No.8 and No.6 particles contain the lowest and second lowest mass fraction of the adsorbate.However,pores were observed in No.6 SiC/Al composite,resulting in a low density in comparison to No.8 SiC/Al composite.After ultrasonic cleaning process,all kinds of the SiC particles could be used to prepare the SiCp/Al composites,with the success rate increasing from 25%to 100%,which could avoid the formation of pores in the infiltrated composites.This indicates that it is very effective to improve the adaptability of the SiC particles to the pressureless infiltration by ultrasonic cleaning method.Consequently,the infiltrating process for preparing SiCp/Al composite could be negatively influenced by the existence of adsorbates on the surface of the SiC particle,which could become worse with increasing fraction of the adsorbates.Mechanical property of No.6 and No.8 composite using original and cleaned SiC particle was investigated.The flexure strength of No.8 composite using SiC particles before and after ultrasonic cleaning is at the same level,being about 370MPa,but the elasticity modulus was improved from 214GPa to 238GPa after ultrasonic cleaning.For No.6 particle,the flexure strength of the infiltrated composite is improved significantly from 322MPa to 392MPa,and the elasticity modulus is improved from 203GPa to 232GPa after ultrasonic cleaning.All of the rest composites using ultrasonic cleaned particles also present good mechanical property,with the average flexure strength being about 380MPa and the maximum value of 400MPa.However,the flexure strength of No.2 composite was only 319MPa.Although the composite,in general,possesses good interface bonding state,few cavities and de-bonding phenomenon near the interfacial region were observed,especially for the composites prepared by the original SiC particles.Fracture surface morphology indicates the cleavage fracture of the SiC particles.Low flexure strength of No.2 composite is because of the fragmentation of the particles due to the internal defects and the fracture at tips of the particles due to stress concentration.