Effect Of GNPs And SiC On The Microstructure And Mechanical Properties Of AlSi10 Prepared By Laser Additive Manufacturing

Due to the advantages of high strength,good wear resistance and low thermal expansion coefficient,composite materials are widely used in transportation,aerospace,energy and power fields.At present,the main research direction in material research is metal matrix composites,and aluminum matrix composites have become the mainstream due to their excellent comprehensive properties and low cost.With the requirements of high speed,lightweight and low energy consumption in the field of transportation,people pay more and more attention to the research of particle reinforced aluminum matrix composites in automobile parts such as automobile piston and brake disc.Due to the high speed friction of automobile brake disc for a long time,wear,brittle fracture and mechanical fatigue failure often occur.This study aims to explore how to achieve higher hardness and better wear resistance,and retain the toughness of the material.In the research process,the micro structure and properties of AlSi10Mg were mainly improved by optimizing its composition.In this study,the effects of solid solution and T6 heat treatment on the microstructure and properties of the samples were also studied.The main content of this paper is to prepare AlSi10Mg,AlSi10Mg+GNPs,AlSi10Mg+SiC and AlSi10Mg+1%GNPs+SiC composite samples by selective laser melting(SLM)technology,and then complete the heat treatment of AlSi10Mg+GNPs samples by vacuum furnace.After the sample preparation was completed,the microstructure and mechanical properties of the samples were observed and measured by X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),microhardness test,friction and wear test and nano indentation test.The experimental results show that when the addition amounts of GNPs are 1%and 2%,the grain size of the sample is significantly refined,and the number of eutectic Si is reduced.This benign change of micro level brings the sample with the improvement of mechanical properties.The micro-hardness is increased by 2.9%～4.4%,and the wear resistance is also improved.The heat treatment temperature is directly proportional to grow grain size.With the solution temperature increasing,the grain length and micro-structure become larger.After solution heat treatment,the hardness of the sample decreased first and then increased.After solution heat treatment at 450℃,500℃ and 550℃,the average hardness of the samples are 101.87 HV,129.36 HV and 149.88 HV respectively.With the increase of heat treatment temperature in the solid solution state,the black spots in the micro-structure of aging composite samples are significantly reduced,and it broken the Si phase in the heat affected zone also.In addition,with the grain growth,acicular eutectic silicon appears in the micro-structure.After complete artificial aging after solution heat treatment,the average hardness of the sample was slightly increased to 109.29 HV,137.23 HV and 130.28 HV,respectively.The friction and wear properties of the samples treated at 500℃ are the best.The ultimate compressive strength of the sample after solution aging treatment at 450℃ is much higher than that of other samples,while the displacement strain curve of the sample without heat treatment is tortuous,and the curve of the sample after heat treatment increases gently,showing good compression properties.After adding SiC ceramic reinforced particles,the distribution is uniform,no obvious agglomeration phenomenon.Through the hybrid enhancement of 1%GNPs+SiC particles,the grain structure changed from coarse columnar grains to fine equiaxed grains and a small amount of short rod grains.The average hardness of AlSi10Mg+5%SiC and AlSi10Mg+1%GNPs+5%SiC composites is the highest,which is 29%and 32.5%higher than that of AlSi10Mg+1%GNPs,respectively.The addition of SiC improves the plasticity of the composite,and the addition of 1%GNPs in SiC composite can make the plasticity of the material uniform.