| AlSilOMg alloy,one of the most widely used alloys in cast aluminum,has excellent casting properties and is applied to cast medium-load parts with complex shapes.Ceramic reinforced aluminum matrix composites are widely used in aerospace,automotive and electronics fields for light weight,high specific strength and high wear resistance.But it is easy to produce obvious defects in aluminum matrix composites by the traditional forming process.Selective laser melting(SLM),as one of the additive manufacturing techniques for metals,has strong material applicability and the advantages of forming composite materials.The parts prepared by SLM have high density and good material properties.In this paper,the effect of SLM process parameters on the density of the AlSi10Mg alloy was studied.The optimal parameters were used to prepare the samples with the highest density.The phase,microstructure,hardness and compression properties of the AlSilOMg sample prepared by SLM were analyzed,and the influence of different heat treatment processes on its microstructure composition and mechanical properties.In addition,TiB2 and SiC ceramic particles were mixed with AlSi10Mg alloy powder and used to prepare composite materials by SLM.The action of different ceramic particles on the phase,microstructure and mechanical properties has been researched and the strengthening mechanism of particle reinforcement was discussed in depth.According to the experiments,under the condition that laser power is 350W,scanning speed is 1600mm/s,layer thickness is 30μm,he hatching space is 120μm,scanning strategy is 670 rotated between two adjacent layers,the density of SLMed AlSi10Mg alloy could reach up to 98.8%.The microstructure of the AlSi10Mg alloy sample was refined and the grain morphology was divided into columnar grains,equiaxed grains and heat affected zones.Due to the grain refinement and solid solution strengthening mechanisms in the SLM process,the microhardness and yield strength could reach 133HV,315MPa,and the plastic strain is 18%.After different heat treatments,the supersaturated Si phase gradually precipitated from the a-Al matrix and grew up.Both the hardness and strength of the heat-treated samples were reduced,but the plastic strain was increased.The submicron AlSi10Mg/TiB2 composite samples formed by SLM has a dentisy of 97.8%.TiB2 particles are evenly distributed in the matrix,and the interface with the matrix is well combined.The TiB2 particles refine the matrix grains,and the pinning effect of TiB2 hinders the grains growing tendency towards the heat flow,promotes the grains to be equiaxed,and improves the anisotropy of material properties.The addition of TiB2 particles effectively improves the hardness and yield strength of the composite,reaching 148HV and 365MPa.Through microstructure analysis,the performance strengthening mechanism includes grain refinement,solid solution strengthening,dispersion strengthening and load transfer mechanism.The AlSilOMg/SiCp composite samples formed by SLM has a dentisy of 98.2%.The SiC particles react with the aluminum melt to form a new strip-shaped A14SiC4 reinforced phase.The SiC and Al4SiC4 phases are evenly distributed in the matrix.The hardness of the composite samples is between 170-200HV,the yield strength reaches 398MPa,and the plastic strain is 22.8%.The fine grains of the microstructure cause fine grain strengthening.The lattice distortion caused by the reinforcement phase and the matrix hinders the movement of dislocations,resulting in dispersion strengthening and solid solution strengthening.The above study established the relationship between the microstructure and mechanical properties of aluminum matrix composites reinforced by TiB2 and SiC particles,and explored the strengthening mechanism of the particle.To further explore the possibility of particle reinforced aluminum matrix composites prepared by SLM. |
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