Microstructure And Mechanical Properties Of Cu-Al Alloy Fabricated By Dual Wire Arc Additive Manufacturing

Cold metal transfer(CMT)technology is a type of wire arc additive manufacturing(WAAM)technology with high material utilization rate,high deposition efficiency,no spatter and low heat input.Compared with traditional manufacturing methods,the high-performance metal parts can be formed economically and rapidly while improving the performance.Copper-aluminum(Cu-Al)composite materials have good electrical and thermal conductivity,corrosion resistance,high strength and high ductility,and it can be made into functionally gradient materials to meet different needs.It has broad application prospects and are widely used in aerospace,shipbuilding and other industries.At present,copper-aluminum alloys were mainly produced by vacuum melting,arc furnace melting,ball milling and other powder metallurgy processes and solid-liquid composite casting technology.Usually,the external protective environment requires more stringent,which increases the cost.The price of metal powder is higher than that of filled wires.In addition,these processes are not suitable for fabricating complex geometric parts.Moreover,these methods could cause defects such as incomplete melting of the powder and reduce the formed part quality.Therefore,low-cost,high-efficiency Cu-Al alloy of WAAM receives people's welcome.In the present work,a new stable and feasible method was used to fabricate Cu-Al alloy by dual wire arc additive manufacturing.Two commercial binary wires namely Cu Si28 L copper wire and ER4043 aluminum wire were fed into the common molten pool to fabricate Cu-Al alloy samples by adjusting the wire feed speeds of two separate wire feeders based on CMT-WAAM.The article analyzed the influence of each process parameters on the forming quality of single-layer single-pass welds by adjusting the process parameters in the manufacturing process,and a set of process parameters with good forming effects are finally determined.The deposited wall was fabricated by dual wire arc additive manufacturing using the selected process parameters.The microstructure of the deposited wall was analyzed by optical microscopy(OM),scanning electron microscopy(SEM),X-ray diffractometry(XRD),electron backscattered diffraction(EBSD).The multi-layered deposited walls at different deposition locations were analyzed.It was found that different microstructures were observed at different deposition locations,and the changes in microstructure depended on heat accumulation and thermal cycling during the process.The deposited wall part showed good integrity and excellent mechanical properties,with only 15 MPa difference in ultimate tensile strength,10 MPa difference in yield strength and 2% difference in elongation among the mechanical properties along the vertical directions.The average microhardness of the lower region,upper-middle region and upper region were 217.1 Hv,226.8 Hv and 221.4 Hv,respectively.The presence of intermetallic compounds leads to fluctuation in microhardness value.Four phases were detected in the deposited wall at different locations.The sample in the vertical direction exhibited superior properties,and the fracture surfaces showed mixed mode characteristics.Investigation was focused on the effect of different deep cryogenic treatment(DCT)holding time on the evolution of microstructure and properties of Cu-Al alloy.It was found that DCT can improve the performance of Cu-Al alloy.In the present work,the DCT conducted for 12 h provided the best properties and economic effects,with relatively high strength and superior ductility.It is due to the relatively small grain size and the random texture formed during DCT process.The grain refinement leads to an increase in grain boundary area,which enhances the ability to resist deformation and thus increases the strength.