Microstructure,tensile Property And Wear Resistance Of SiCp/AlSi7Mg Composite Fabricated By Selective Laser Melting

With the improvement of the comprehensive performance requirements of materials in the fields of aerospace,automotive and shipping,metal matrix composites are widely used in various fields because of the comprehensive performance of metal materials and reinforced materials.SiC particle reinforced aluminum matrix composites have excellent electrical conductivity,thermal conductivity,corrosion resistance,high specific strength,which have been applied in aerospace and other fields.However,with the increasing demand of modern industry for lightweight and integrated structure,traditional processing methods are difficult to meet the manufacturing requirements of complex and precise structures such as the structures with thin-wall and integrated intakes.Selective laser melting（SLM）technology uses high energy laser beams to melt metal powder layer by layer,which can directly obtain solid parts with complex structures and good performance.The application prospects of SLMed particle reinforced aluminum matrix composite are board.In this paper,SiC particle and AlSi7Mg alloy powder are used as raw materials to study the influence of different process parameters and SiC mass fraction on the relative density of SiCp/AlSi7Mg composite samples fabricated by SLM.The SLMed SiCp/AlSi7Mg composite relative density could reach to 99.2%at the optimal process parameter.The phase composition,microstructure,tensile properties,microhardness and wear resistance of composite are characterized.The influence of the reinforcement on the microstructure and mechanical properties of composite is also investigated.The relationship between the forming quality,the microstructure and the mechanical properties of SLMed sample is analyzed.The main research contents and results are as follows:First,the effect of process parameters and reinforcement phase content on the forming quality of SLMed SiCp/AlSi7Mg composite samples is studied.It can be found that the pore defects inside the sample first decreases and then increases with the increase of scanning speed and hatch spacing,and the relative density of the sample first increased and then decreased.When the laser power is 300W,the scanning speed is 1400mm/s,the hatch spacing is 0.12 mm and the layer thickness is 30μm,SLMed SiCp/AlSi7Mg composite with a relative density of99.2%can be obtained.With the enhancing of the SiC content,the relative density of sample also shows a trend of first increasing and then reducing.The relative density is the highest when the SiC mass fraction is 5 wt.%.Secondly,the microstructure and the mechanical properties of 5 wt.%SiCp/AlSi7Mg composites are analyzed.Because of the high temperature of molten pool in the SLM process,some SiC particles react with Almelt to produce new needle-like Al₄SiC₄ reinforcing phase which distribute in Almatrix and the interfaces of SiC and matrix.This forms a good metallurgical bonding between reinforcements and matrix.With the laser energy density enhanced,the amount of SiC reduces due to the improvement of in-situ reaction extent,and the mechanical properties show a trend of increasing first and then decreasing.When the laser energy density is 59.52 J/mm³,the sample performance reaches a peak value.The tensile strength,yield strength and elongation are 452 MPa,280 MPa and 4.5%,respectively.The microhardness of composite is 148.4 HV,and the average friction coefficient and wear rate are0.45 and 4.91×10^-5 mm³N^-1m^-1.Finally,the influence of SiC mass fraction on the microstructure and mechanical properties of SLMed SiCp/AlSi7Mg composite samples are also investigated.With the increase of SiC content,the tensile strength of sample increases first and then decreases,however,the elongation decreased significantly.The microhardness first raises and then declines,and the average friction coefficient and wear rate first enhances and then reduces.The microstructure uniformity and forming quality of SLMed composite are the main factors which affect the mechanical properties of sample.When the mass fration of SiC is too low or too high,the relative density and uniformity of composite sample microstructure are poor,and its mechanical properties reduce.