Study On The Process And Properties Of TiB₂/AlSi10Mg Composites Fabricated By Selective Laser Melting

Selective Laser Melting（SLM）technology is currently one of the most advanced manufacturing technology.Considering that the wide application of aluminum alloy in aerospace and automobile,the research on SLM technology has attracted great attention.However,the forming quality of SLM is seriously affected by the aluminum alloy powder with low laser absorptivity and high thermal conductivity.The method of adding ceramic particle reinforcement phase into aluminum alloy is generally used to improve the forming quality of SLM and mechanical properties,which provides a new approach to form fully dense and high performance aluminum alloy parts.Therefore,in this paper,AlSi10Mg alloy was selected as the matrix and TiB₂ ceramic particles as the reinforcement phase,in order to improve the forming quality of TiB₂/AlSi10Mg composites fabricated by SLM and their mechanical properties.The main research contents and conclusions are as follows:（1）The influence of process parameters on the forming quality of TiB₂/AlSi10Mg composites adding different contents of TiB₂ was studied,and the effect of laser power and scanning speed on the relative density,surface defect,surface morphology and molten pool morphology of the samples was explored to obtain the optimum process parameters.The optimum laser power and scanning speed for TiB₂/AlSi10Mg composites with 1%TiB₂ are250W and 1400mm/s,respectively,and the relative density can reach 99.5%,the surface roughness is 21.7μm.The relative density is increased by 0.9%and the surface roughness is decreased by 36.7%as compared to AlSi10Mg ally without adding TiB₂.（2）Aiming at the TiB₂/AlSi10Mg composite fabricated by SLM with the optimum process parameters,the effects of TiB₂ content on the microstructure,phase composition,element distribution,surface morphology and microhardness of the composites were studied,and the strengthening mechanism of TiB₂ ceramic particles was revealed.The results show that the addition of TiB₂ enhanced phase changes the microstructure from dendritic dendrites to equiaxed crystal,the grain is refined without generating new phase,the optimal crystal orientation is changed,and the surface spheroidization phenomenon is improved,and the microhardness is increased.The microstructure of the composites is finer,the surface morphology is better and the microhardness is higher as the content of TiB₂ is 1%.（3）Remelting treatment was studied on the typical pore defects of AlSi10Mg alloy fabricated by SLM,and the mechanism of laser remelting process for improving internal defect and surface morphology was revealed.Furthermore,the laser remelting treatment of TiB₂/AlSi10Mg composites was studied.The results show that the laser remelting treatment can eliminate the lack of fusion holes,reduce the gas pores and keyholes,and improve the forming quality of AlSi10mg alloy.The surface morphology of TiB₂/AlSi10Mg composite fabricated by SLM is significantly improved after laser remelting,and the surface roughness is decreased by 51.7%from 21.7μm to 10.4μm.remelting.The microstructure of the remelted composite is finer and the microhardness is increased by 8.7%in comparison with that of non-remelted composite.