Experimental Study On Nickel Film With Heterogeneous Laminated Structure By Wire Anode Scanning Electrodeposition

The strength-ductility balance of nanostructured metallic materials has always been one of the research hotspots in the field of materials.As the grain feature size decreases to the nanometer scale,nanocrystalline materials exhibit excellent tensile strength,but their ductility deteriorates due to the multiplication of grain boundaries and reduced strain hardening ability.Introducing structures such as stacks/gradients/doublets inside nanomaterials has proven to be an effective way to solve the trade-off between strength and ductility.In this paper,in view of the shortcomings of the existing electrodeposition for the preparation of heterogeneous laminated nanostructured metal materials,a variable-speed displacement wire anode scanning electrodeposition technology for heterogeneous laminated nanostructured materials is proposed to prepare high strength,high toughness and high purity metal nanostructured materials with simple,efficient and low cost.The main research contents and innovations of this paper are as follows.On the basis of analyzing the working characteristics and working principle of wire anode scanning electrodeposition,the mathematical model between wire anode scanning speed and critical stable nucleation free energy was deduced,and the intrinsic correlation between scanning speed and grain size was proved.The microstructural characteristics of the laminated interface formed by different stacking orientations(same orientation(0°),dislocation(45°),orthogonal(90°))and different thicknesses of microcrystalline/nanocrystalline layers and their effects on mechanical properties The influence mechanism of microcrystalline layer thickness,nanocrystalline layer thickness,number of layers,stacking orientation,stacking method,etc.on the mechanical properties of laminated materials was analyzed,and the goal was high strength and good ductility under the constraint of constant thickness The above parameters and conditions are optimized.The results show that the micro-crystalline layer(200-300nm)and nanocrystalline layer(15-50nm)with the scanning speed of 0.1mm/s and 10mm/s have the best interfacial adhesion and comprehensive mechanical properties(tensile strength is522.7MPa,fracture ductility is 11.7 %).Under the condition that the number of layers is4,the tensile strength of the four-layer structure nickel film with the thickness ratio of nano-crystalline layer to micro-crystalline layer r=4/16 to r=16/4 is 19.8% higher than that of the four-layer structure nickel film with equal thickness r=10/10,and the fracture ductility is increased by 8%;among all even layers,the hardness of the heterogeneous multi-layer structure specimen with 8 layers is 584 MPa,the tensile strength is as high as615 MPa,and the fracture ductility is 17.4%.Compared with the same thickness nanostructured materials,the fracture ductility is increased by 89.7%(2.8%),while the tensile strength is only decreased by 6.8%(660MPa).The mechanism of local micro-shear band surge caused by the increase of interface number on the mechanical properties is revealed.Different stacking directions can effectively improve the anisotropy of mechanical properties caused by the scanning direction of the wire anode.The dislocation and orthogonal stacking make the tensile strength difference index of each direction decrease from 19.46% to 5.22%(8layers),and the fracture ductility difference index decrease from 40.21% to 7.76%(8layers),and the difference can be further reduced by increasing the number of layers.