Immersion Ni Coating Structure Characteristic And Its Effects On The Interface Of Al/Cu Bimetal

Clad material is a newly arisen material which can effectively integrate the advantages of two substrate materials, so it is widely used in many fields of modern industries, such as national defense, aviation, automobile and electric power. At present, the most commonly used clad materials are aluminum/aluminum, aluminum/copper, aluminum/magnesium and steel/aluminum materials. However, brittle compounds often form at the interface of dissimilar bimetal materials due to the reaction between the two substrates, which seriously affect the performance of the material, thus adding a new interlayer with stable performance at the interface to inhibit or slow down the generation of brittle compounds is of great significance.This paper improved the bonding interface properties by combining the immersion plating technology and traditional preparation technology of bimetal materials, i.e. making immersion nickel plating on aluminum surface before bonding with copper substrate and finally, a new aluminum/copper clad material with nickel interlayer was prepared. On the basis of above results, the scanning electron microscope, X-ray diffraction, electron probe, microhardness tester and electronic tensile tester were employed to study the nickel interlayer structure characteristic and its effects on the interface structure and properties of aluminum/copper clad materials.This experiment prepared immersion nickel coating on the surface of aluminum alloy by immersion solution with400g/L NiCl2,50g/L H3BO3and25ml/L HF, the plating time is2min,4min,6min,8min,10min and12min, respectively. The results show that the nickel coating exhibits a bud shaped structure with satisfactory quality. With prolonging the immersion time, the coverage rate of nickel coating on the substrate surface increases, surface defects decrease, the coating exhibits good continuity and surface uniformity, the growth curve of the coating finally follows parabolic growth laws. Thermal shock test is carried out to test the bonding force of the coating. The result shows that the coating does not appear chipping or peeling phenomenon after thermal shock, which indicating the good combination between coating and substrate.A traditional kind of aluminum/copper clad material and a new kind of aluminum/nickel/copper clad material were prepared at diffusion temperature of450℃,500℃,550℃and diffusion time of30min.The result shows that the nickel interlayer changes the interface composition of aluminum/copper clad material, the interface component changes from three kinds of Al2Cu, AlCu, Al4Cu9intermetallics into two kinds of Al3Ni, Al3Ni2intermetallics and Ni-Cu solid solution, and the thickness of the compound greatly reduces. The tensile shear strength of specimens are improved by adding nickel interlayer, the highest bonding strength of the samples increases from14.30MPa to34.70MPa, and the fracture mode of the clad material transforms from single brittle fracture to brittle and ductile fracture mode.