Experimental Study On Metal Additive Manufacturing By Selective Electrochemical Deposition

With the popularization and application of additive manufacturing technology,additive manufacturing of metals has rapidly developed into one of the most promising advanced manufacturing technologies in the field of additive manufacturing,and it has an increasing proportion in the field of metal processing in China,showing great potential.Among them,the additive manufacturing of crystalline metals develops most rapidly,and the main technologies include selective laser sintering and selective laser melting,etc.The existing additive manufacturing technologies for metal parts require expensive lasers and inert gas protection,etc,which have high costs and strict requirements on the operating environment.Electrochemical deposition is a typical additive processing method,which can realize the electrochemical additive manufacturing of metal by combining the electrochemical deposition technology and additive manufacturing technology.In this paper,the composite conductive materials of polylactic acid（PLA）and carbon nanotubes（CNTs）were used as the selective electrochemical deposition substrate.Combined with the electrochemical deposition technology,the 3D metal forming was realized.The effects of CNTs content on the mechanical strength,resistivity and electrochemical deposition of PLA-CNTs composites were studied.The local conductive sample prepared by a double-nozzle 3D printer was combined with the electrochemical deposition technology to realize the metal and multi-metal forming.The specific research contents and results of this paper are as follows:（1）Polylactic acid/carbon nanotube composites were prepared.PLA and CNTs at different proportions were evenly mixed and then extruded to prepare PLA-CNTs composites suitable for 3D printing.The effects of CNTs content on tensile strength,bending strength and resistivity of composites were studied.The experimental results show that the tensile strength,bending strength and resistivity of the composites decrease with the increase of CNTs content.Through comparative experiments,PLA-CNTs_7%wtwas selected as a conductive plastic with good mechanical properties,low resistivity and easy processing.The conductive plastic can be used as cathode substrate material for electrochemical deposition.（2）A local conductive sample composed of PLA and conductive plastic(PLA-CNTs_7%wt)was prepared by using a dual-nozzle 3D printer,and the conductive region（conductive plastic）and insulating region（PLA）were reasonably distributed.The sample was selectively deposited in the electrolyte and the plastic substrate was removed to achieve 3D metal forming.The influence of deposition time on sample surface morphology and sample quality was investigated.The method of preparing metal samples in array is adopted to improve the processing speed of metal samples and provide an effective method for realizing additive manufacturing of metal parts and mass production.The influence of sulfuric acid and polyethylene glycol content on the surface morphology and quality of samples was investigated.Cu-Ni two-layer metal samples and four-layer metal samples were prepared to realize multi-metal additive manufacturing.There were no pores,cracks and delamination at the interface of the two kinds of metals in the samples,and the forming quality of the samples was good.According to the difference of thermal expansion coefficient of the two metals,the 4D printing of bimetallic samples was preliminarily investigated.（3）Electronic components composed of plastic substrate and conductive metal were prepared by selective electrochemical deposition.The results show that the electronic components prepared by this method have excellent electrical conductivity.The influence of two printing directions on the width of conductive region of sample is studied.It is found that the minimum effective design width of the conductive region is0.2 mm,the actual width is about 132.4μm,and the deposited copper wire width is about 183.2μm,which realizes the preparation of micron electronic circuit.A hollow spiral coil was prepared to demonstrate how to create a powerful 3D electrical device,and the inductance,impedance and electromagnetic properties of the spiral coil were tested.Electrochemical deposition of various metals in different parts of the same component,for example,allows active zinc and inactive copper to be incorporated into the same component to produce a copper-zinc battery.