Research On The Method And Characteristics Of Wire And Arc Additive Manufacturing Of High Strength Aluminum Alloys Based On Mutual Melting Technology Of Muti-wires

High strength aluminium alloy is widely used in the aviation field,such as fuselage skin,fuselage longitudinal beam,lower wing skin,wing box inner wing beam,etc.However,the large size and complex structure of aeronautical integral structural parts have posed great challenges to the traditional process of material reduction and other materials.WAAM takes continuous wire as its basic configuration unit.It has low cost,high deposition efficiency,low material removal rate,and its forming size is not limited by the forming cylinder.It is especially suitable for the rapid forming process of large size and complex shape components.It has great application potential and advantages in the aviation field.However,high-strength aluminum alloy has high strength and poor plasticity,and it is difficult to draw wire directly.Therefore,this paper proposes a manufacturing method of high strength aluminium alloy additives based on heterogeneous multi-wire co-melting.Aiming at Al-Mg-Cu alloy and Al-Zn-Mg-Cu alloy,the design of multi-wire additives manufacturing system,the method of composition control and the analysis of structure and properties were studied.Firstly,according to the characteristics of multi-wire eutectic process,a multi-wire eutectic platform based on TIG fuse process is designed and developed,including fuse unit,motion unit,signal acquisition unit and interface display unit,so as to realize flexible design and additional material manufacturing of mult-elemental alloy.Secondly,in order to meet the requirement of the structure and performance of multi-wire reinforced components,the location of multi-wire and current type were explored.On this basis,the influence of deposition speed and current on the structure and performance of the components was studied from two levels of single-layer single-channel and single-wall,and the process window of multi-wire reinforced aluminum alloy was obtained.Then,two kinds of twin-wire eutectic systems,Tandem-based twin-wire eutectic augmentation manufacturing system and TIG-based twin-wire eutectic augmentation manufacturing system,were successfully designed and obtained Al-2.4Mg-3.2Cu alloy?close to 2A02 aluminum alloy?by controlling the wire feeding rates of ER2319 and ER5356.The composition and phase composition were in line with the expected design.The mechanical properties test showed that the maximum tensile strength of single-wall components obtained by TIG twin-wire co-melting additive manufacturing system can reach 280 MPa,which is better than that of single-wall components?256 MPa?obtained by Tandem twin-wire additive manufacturing system.The average hardness of the two components has little difference,but the hardness distribution of single-wall components obtained by Tandem twin-wire system fluctuates obviously and has many low hardness discrete points.Microstructure observation showed that Tandem twin-wire system had more pore in single-wall wall,which affected the stability of mechanical properties of components.Finally,based on TIG multi-wire material additive manufacturing system,by controlling the wire feeding rates of ER2319 and ER5356 welding wires and pure Zn wires,as-cast Al-2.6Mg-2.6Cu-6.6Zn alloy?approaching 7050 aluminum alloy?was successfully designed and obtained.The components were mainly composed of?-Al,S phase?Al₂CuMg?,?phase?MgZn₂?and?phase?CuAl₂?,and the phase composition and composition errors were in line with the expected design.The microstructure of the component was divided into two parts:innerlayer zone and interlayer zone.The bottom part of the interlayer zone was mainly composed of columnar crystals,and the upper part was mostly equiaxed crystals,which conforms to the grain growth law under the heat distribution characteristics of the molten pool.There are a few fusing defects such as porosity and cracks in the interlayer zone.The results of mechanical properties test showed that the hardness of the component fluctuates in the range of 95HV-115HV,the highest tensile strength in horizontal direction is 241 MPa,and the highest in vertical direction is 160 MPa,showing typical anisotropy,which is mainly caused by the fusion defects in interlaminar zone.