Research On Aluminum Alloy Manufacturing Process And Properties Using Wire Arc Additive Manufacture Based On Cold Metal Transfer (CMT)

Wire arc additive manufacture（WAAM）is a digital technology that directly manufactures complex metal parts by depositing materials layer by layer with arc as heat source and metal wire as filler.Because of its potential advantages of saving time and cost,it has attracted great attention and has been applied in aerospace,shipping,industrial manufacturing and other fields.At present,metal-based additive manufacturing is mainly based on high-energy beam technology,such as laser、plasma arc and electron beam.These technologies have reached a high degree of maturity and have been commercially practiced.However,their cost-intensive,very high precision and instrumentation requirements,as well as special environments such as vacuum in electron beam melting,limit their using in manufacturing medium to large components.Wire arc additive manufacture technology provides a new alternative method for high energy beam-based additive manufacturing.Aluminum alloy is widely used in wire arc additive manufacture as a nonferrous metal structural material in industry.The special physical and chemical properties of aluminum alloys,such as high affinity to oxygen,low melting point,high thermal conductivity and high thermal expansion coefficient,make it difficult to realize the additive manufacture of aluminum alloys.Among them,there are still some problems such as porosity,inclusions,hot cracks,serious flow of additive manufacturing and insufficient metal properties after forming.Pore and poor forming accuracy are the most common defects in aluminum alloy WAAM.In this paper,the cold metal transfer（CMT）based wire arc additive manufacture（WAAM）technology for aluminum alloy is used to systematically study the forming size,pool dynamics,porosity,microstructure and properties of aluminum alloy samples.The main research work in this paper was as follows:（1）The wire arc additive manufacturing system based on cold metal transfer was introduced,which was composed of FANUC robot operating system and three-dimensional path simulation software（3D Printing）.（2）Al-Si welding wire（ER4043）was used as filler metal to study the forming law of single-layer and single-pass samples by changing wire feed speed（WFS）or travel speed（TS）or torch angle（WT）.When travel speed was 0.6m/min,wire feed speed was 7.0m/min,torch angleαandβwere both 90°,the forming surface of single-layer single-pass deposited bead was smooth,without spatter,hump,undercutting and other defects,and the forming size of deposited bead was moderate,the forming quality was good,but the porosity was high.When the torch angleαandβwere deviated to 90°,porosity and pore’s size and defects could be effectively reduced,a better comprehensive deposited bead was gotten.（3）Al-Mg alloy parts were manufactured by wire arc additive manufacturing system based on cold metal transfer technology.Al-Mg welding wire（ER5356）was used as filler metal to fabricate Al-Mg alloy components with different heat input by adjusting wire feed speed（WFS）and travel speed（TS）.The macro-morphology and microstructure of thick-walled samples were characterized by optical microscope（OM）,X-ray diffraction（XRD）,scanning electron microscope（SEM）with energy dispersive spectroscopy（EDS）,and vickers hardness and tensile properties were studied.When WFS was 7.0 m/min and TS was 0.9m/min,the grain size in the inner layer was 42.9-88.7μm,and the grain size in the inter layer was 37.7-77.6μm,while the grain size in the same region was larger in other different WFS/TS.The main metallographic phases wereα-phase（Al）andβ-phase（Al₃Mg₂）.The phase composition was significantly affected by WFS and TS.The mechanical properties of samples under different WFS/TS were relatively stable,and the average micro-hardness showed homogeneous characteristics of 70-77Hv.The ultimate tensile strength（UTS）,yield strength（YS）and elongation（E%）were 255±5MPa、128MPa and 23.2%respectively.For all samples,the fracture exhibited typical ductile fracture characteristics.（4）Using CMT/CMT+Advance mode and 3D Printing slicing software,the complex Al-Si alloy parts were fabricated by additive manufacturing.The size of droplet,the forming size of parts and the stability of parts manufactured by wire arc additive manufacturing system based on cold metal transfer technology were analyzed.