| Aluminum alloy has the advantages of low density,good thermal conductivity,corrosion resistance,high specific strength,as well as excellent plasticity and relatively low manufacturing cost,etc.It enjoys a wide range of market applications,especially in areas that are sensitive to quality factors,such as aerospace,military,and automotive manufacturing.At present,with the rapid development of China’s industry,aluminum alloy parts have gradually shown a development trend of light weight structure and composite performance.In actual applications,the requirements for part performance and production efficiency are higher.Traditional subtractive manufacturing technology(such as casting,forging,etc.)has been difficult to meet these manufacturing needs.Additive manufacturing is a bottom-up layer-by-layer manufacturing method.With its special forming method and high flexibility,it can achieve the purpose of lightweighting in both material weight reduction and structure weight reduction.At present,in the research process of aluminum alloy additive manufacturing,due to the shortcomings of aluminum alloys such as strong oxidation,low laser absorption,and wide solidification temperature range,a tough oxide film is easily formed on the surface of aluminum powder,which hinders metal connection between layers,thereby affecting the density and performance of the formed part.In addition,aluminum powder has poor fluidity and high laser reflectivity,which can easily cause pores and cracks,making it difficult to significantly increase the strength and plasticity of additive-manufactured aluminum alloy parts.In response to the above problems,scholars at home and abroad have conducted a lot of research to improve the microstructure and mechanical properties of additive-manufactured aluminum alloy parts through decoration,process optimization,and heat treatment.Currently used in the market for additive manufacturing aluminum alloys are Al-Si series(such as AlSi10Mg,AlSi 12),Al-Cu series(such as Al2024),Al-Zn series(such as A17075)aluminum alloy powder for Selective Laser Melting additive manufacturing,and Al-Mg series,Al-Li series aluminum alloy wire for Wire and Arc Additive Manufacturing.The decoration treatment includes the addition of rare earth elements(such as Sc,Zr,etc.)or nanoparticles(such as TiC,TiB2,SiC,etc.)to improve the fluidity and compactness of the aluminum alloy powder and the microstructure of the formed part,thereby increasing the mechanical properties of the formed part.However,the above methods are restricted by factors such as high cost or complicated metallurgical process,with a low performance cost ratio.Therefore,under the premise of ensuring performance,how to simplify the process,reduce costs,improve efficiency,and expand aluminum alloy powders that are suitable for additive manufacturing has become the main development trend.In addition,compared to the research on Selective Laser Melting of aluminum alloy powder,there is less research on Wire and Arc Additive Manufacturing.In addition,because of the large heat input and the low stability of the forming process,it is difficult to improve the microstructure and mechanical properties of the formed part.Therefore,it is an urgent problem to improve the quality and performance of aluminum alloy formed part produced by Wire and Arc Additive Manufacturing.This research mainly studied Selective Laser Melting additive manufacturing process of aluminum alloy powder materials.Powder materials applied include AlSilOMg,A17075 and A12024 powder.AlSilOMg was decorated with Al-Ti-C-B master alloys with content of 1 wt.%,5 wt.%,10 wt.%and 20 wt.%respectively,by mechanical mixing.The modification effect of nano-TiC particles and nano-TiB2 particles on the additive-manufactured AlSilOMg formed part was investigated,aiming to refine microstructure and improve mechanical properties.Al7075 was decorated with 10 wt.%Al-Ti-C-B master alloys by mechanical mixing,and the effect of nanoparticles on the microstructure and mechanical properties of Selective Laser Melting additive-manufactured A17075 was observed.Al2024 was decorated with 1.5 wt.%TiC particles by in-situ reaction,and the effect of this process on the microstructure and properties of additive-manufactured A12024 was explored.The purpose is to promote nucleation and improve the printability of the alloy by introducing modifiers.At the same time,this research also conducted a certain degree of research on the Wire and Arc Additive Manufacturing of aluminum alloy wire,employing metal wire including AI-Mg alloys and Al-Li alloys.By adding 0.22 wt.%Sc to A15356 composition,the effect of Sc on the grain refinement,tensile strength and ductility was investigated.Wire and Arc Additive Manufacturing of Al-Li alloy wire and the solution aging heat treatment of the formed part were conducted.The effects of additive manufacturing process and different heat treatment systems on the microstructure and properties of the alloy were explored.The experimental results show that for the Selective Laser Melting additive manufacturing process of aluminum alloy powder,the Al-Ti-C-B master alloy significantly refines the microstructure of AlSi10Mg alloy,and the average grain size is reduced to less than 3μm.When the doping amount of the refining agent is 1-5 wt.%,the tensile strength reaches 500-520MPa,and the elongation is about 12-15%.Continuing to increase the amount of doping can further refine the grains and increase the elongation slightly,but the tensile strength decreases.The doped Al-Ti-C-B master alloy can also inhibit the growth of columnar crystals of A17075 aluminum alloy,transform them into fine equiaxed crystals,and eliminate anisotropy.However,since thermal cracks still exist,mechanical properties cannot be improved.The in-situ doped Al-Ti-C master alloy optimizes the A12024 aluminum alloy additive manufacturing printability and eliminates microcracks,but the grain refinement is still not enough to improve the mechanical properties of the alloy.For Wire and Arc Additive Manufacturing process of aluminum alloy,the addition of 0.22 wt.%Sc significantly refines the microstructure of A15A06 aluminum alloy,obtaining equiaxed grains with an average grain size of 40μm.The tensile strength reaches 290MPa and the elongation reaches 36%.For Al-Li alloy wire,the additive manufacturing process remarkably improves its microstructure,from columnar crystals to equiaxed crystals,and solution treatment further improves its tensile strength and elongation. |
