Study On Process And Properties Of TPMS Structure AlSi10Mg Alloy Fabricated By Selective Laser Melting

Lightweight design is crucial to the performance improvement of aerospace equipment and its economy,safety and reliability.Porous aluminium alloys has attracted great attention of scholars both at home and abroad,due to their dual advantages in lightweight structure and material.In the design of porous structures,the triply periodic minimal surfaces（TPMS）structure is a porous structure with good controllable performance,large specific surface area and smooth pore surface,which possess bionic characteristic,and become a hot research topic.Selective laser melting（SLM）technology is one of the additive manufacturing technologies which can be used for the precise processing of complex pores for TPMS structures.In addition,the lightweight aluminium alloys fabricated by SLM is much more difficult than other metals due to their low laser absorption,high thermal conductivity,poor powder flow and high temperature oxidation.However,AlSi10Mg alloy has good SLM forming processability,low thermal expansion coefficient and good corrosion and wear resistance.Therefore,forming process and properties of AlSi10Mg alloy with TPMS structure fabricated by SLM,and the main research contents and conclusions are as follows:（1）The influence of process parameters on the denseness and pore defects of AlSi10Mg alloy fabricated by SLM was investigated,the forming mechanism of pore defects was revealed,and the microstructure and its influence on microhardness were clarified.The results show that the relative density of AlSi10Mg alloy samples fabricated by SLM are related to the linear and volumetric energy densities.When the linear and volumetric energy densities are low,lack of fusion pores are easily formed because the overlap of the adjacent melt pool is poor.And when the linear and volumetric energy densities are low are high,keyholes are easily formed because the gas is involved in melt pool and is difficult to escape.The microstructure of different areas of AlSi10Mg alloy fabricated by SLM is significantly different,microhardness of the fine grain is higher due to its fine and dense structure,which is122.8 HV_0.1.（2）The SLM forming process of AlSi10Mg alloy with TPMS structure was investigated and the influence of the process parameters on the forming quality and dimensional accuracy was investigated.The results showed that the relative density of TPMS structured AlSi10Mg alloy fabricated by SLM can reach 99.8%with 200 W laser power and 1750 mm/s scanning speed（the line energy density is 0.12 J/mm and the bulk energy density is 40.82 J/mm³）.The wall thickness of the curved surface and the morphology of the top and bottom surfaces are significantly different,which depends on the laser energy density and angle.The higher the laser energy density,the greater the difference between the top and bottom surface morphology,and the wall thickness is thicker.Furthermore,the difference between the top and bottom surfaces decreases as the angle increases,which is the largest as the angle is 0°,and the wall thickness is the thickest.（3）The compression and energy absorption properties of three typical TPMS structures were studied,including Primitive,Gyroid and Diamond types,and their anisotropy in the additive and horizontal directions was investigated.The results show that the elastic modulus,yield stress and compressive strength of the Diamond TPMS structure are the largest as compressed in the building and horizontal directions,and the anisotropy is the most obvious.the compression performance in the building direction is significantly higher than that in the horizontal direction,and the energy absorption in the building direction is 239.07 MJ/m³higher than that in the horizontal direction.