| Due to its high strength and low density,Aluminum Matrix Composites（AMCs）has been widely used as lightweight alloy in many fields.Selective Laser Melting（SLM）technology is suitable for the fabrication of complex structural components.AMCs prepared by SLM technology have great suitability in aerospace,medical and military fields.But owing to the research of SLM technology staring late in China,there are still a lot of problems existing in SLM preparation of AMCs.First,aluminum alloy powders are easy to oxidize,which makes SLM formation is difficult.Secondly,as strengthening phase for strengthening mechanism of composites,addition of the secondary phases will further increase the forming difficulty,Due to the above two problem,this paper utilized SiC powder and AlSi10Mg alloy powder as raw material to,fabricate AMCs reinforced by SLM.The effects of phase mass fraction SiC particle size and processing parameters of SLM on the microstructure and performance were studied,and the effect of the heat treatment on performance of AMCs composites was also investigated for getting more superior material properties.Firstly,the effect of small SiC mass fraction on the microstructure and properties of AlSi10Mg alloy was studied.Samples were prepared at different laser scanning speeds.Microstructure of AlSi10Mg alloy is in the shape of a molten pool.Under normal circumstances,the morphology of the molten pool is in the shape of a long strip.The molten pool is wide in the middle but narrow at both ends.With increasing SiC mass fraction,the weld pool width increases.Small particles SiC with particle size smaller than 10 microns increase the hardness and wear resistance of AlSi10Mg alloy.With increasing mass fraction,the enhancement effect becomes more obvious.When 2%small SiC is added,the microhardness increases from 150.0 HV to 170.8 HV,the friction coefficient increases from0.410 to 0.436,and the wear rate also decreases.When the small SiC mass fraction increases to 5%,the hardness and wear resistance of the AlSi10Mg alloy are further improved,the surface hardness of the material reaches 180.9HV,the friction coefficient of the material reaches 0.330,and the wear rate of the 5%SiC reinforced AlSi10Mg alloy is the lowest with the value of 2.1×10-9.The compressive strength of AlSi10Mg alloy decreases with increasing mass fraction of small SiC,and the ultimate compressive strength decreased from 720 MPa to380 MPa.According to phase analysis,after the addition of small-particle SiC to AlSi10Mg alloy,under the effect of laser,the new AlSi and Si phases are generated during SLM processing.Moreover,with increasing SiC mass fraction,a brittle Al4C3 phase was detected in the composite material.This phase is brittle,which seriously affects the comprehensive performance of the alloy.When using SiC with different particle size to strengthen AlSi10Mg alloy,it is found that SiC particles with size of about 50 micrometers have better effect on alloy strength,hardness and plasticity than those with particle size of about 10 micrometers,after adding larger particles SiC,alloy microhardness decreases to 150.0HV from 166.5HV.The addition of large SiC increased the tensile strength of AlSi10Mg alloy.After the addition of 2%large particle SiC powder,the tensile strength reached 379.8MPa and the elongation was 5.20%,while the ultimate tensile strength of AlSi10Mg alloy without reinforcement phase was only331.1MPa and the elongation was lower.Compared with microhardness and wear resistance,the improvement of tensile strength and plastic toughness of AMCs materials is more significant for engineering application.Therefore,solid solution heat treatment was carried out on large particle SiC reinforced AlSi10Mg alloy,and AlSi10Mg alloy without SiC reinforced phase was selected for comparison in order to further enhance the plastic toughness of the alloy on the original basis.The heat treatment method was solid solution heat treatment.The furnace temperature was heated to 400℃and the samples were put into the furnace for 1.5 hours,followed by water cooling to room temperature.After analyzing the microstructure of the AlSi10Mg alloy with heat treatment,it was found that the failure strain of AlSi10Mg alloy without SiC reinforcement was significantly improved,but its tensile strength and hardness decreased,and the fracture mechanism changed from the original brittle fracture to plastic fracture.However,the failure strain,strength and hardness of AlSi10Mg alloy strengthened by SiC decreased.During the heat treatment,the Si phase combined with Al by laser action was precipitated again,and the number of AlSi phase in the material decreased.It is proved that the solid solution heat treatment process is not suitable for AlSi10Mg alloy after adding SiC. |
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