Study On The Process And Mechanical Properties Of TiN/AlSi10Mg Composites Fabricated By Selective Laser Melting

AlSi10Mg powder has high reflectivity under infrared laser,energy loss makes SLM forming difficult.Studies have shown that it is an effective way to improve the properties of aluminum alloy by preparing composites.Ti N powder and AlSi10Mg powder were used as raw materials to prepare Ti N/AlSi10Mg composites by SLM technology,the influence of Ti N particle mass fraction on the microstructure and properties of the composites was studied,and a statistical model of the influence of process parameters on density was established by response surface method.The main research contents are as follows:First,Ti N/AlSi10Mg composites with different Ti N additions（0 wt.%,1 wt.%,3wt.%,5wt.%）were prepared in situ by selective laser melting.The effects of Ti N content on the densification,microstructure evolution,crystal textures,and mechanical properties are investigated.Results show that the relative density of composite samples with 0–3 wt.%Ti N is higher than 98%while the Ti N particles are distributed uniformly and wetted with the AlSi10Mg matrix in the form of graded interfacial layer.Further increasing Ti N content resulted in a decrease in their relative density.Compared with the AlSi10Mg alloy,the microhardness,tensile strength and wear resistance of Ti N/AlSi10Mg composite are improved.The optimal Ti N content is found to be 3 wt.%,the average grain size is 2.67mm,at which the fabricated samples exhibit excellent mechanical performance（132.4 HV for hardness and 379.7MPa for tensile strength）with a low friction coefficient of 0.49.Furthermore,the laser absorptivity,forming process and mechanical properties of 3 wt.%Ti N/AlSi10Mg composite powder were studied.The statistical model of the influence of process parameters on the density was established by response surface method and ANOVA.The optimal process parameters predicted by the model are laser power of 200 W,scanning speed of 1300 mm/s,scanning distance of 0.14 mm,powder thickness of 0.03 mm.Ti N plays the role of dispersion strengthening and fine grain strengthening during the formation of microstructure.The microhardness is136.2 HV,the tensile strength is 397.7 MPa,the elongation is 12.5%,the friction coefficient is 0.41,indicating that the mechanical properties of AlSi10Mg with Ti N addition are improved.Finally,in order to further improve the mechanical properties of the sample and eliminate the residual stress during the forming process,different heat treatment processes（direct aging,stress relieving,T6）were selected to regulate the structure of the composite sample.After aging treatment at 160 ^oC for 6 h,the optimal mechanical properties were obtained,and the residual stress was greatly reduced,and the precipitation of nanoscale Si phase and Mg₂Si strengthened phase was promoted.The mesh eutectic Si structure was basically retained,with the hardness of 143.5 HV,the tensile strength of 408.7 MPa and the elongation of 15.3%.The residual stress was significantly reduced,with a decrease of 78.9%.