Research On Interfacial Behaviors Of Al/Ni/Cu Composites

Aluminum-copper composites not only have good electrical conductivity,thermal conductivity and low contact resistance,but also have the characteristics of light weight,excellent heat dissipation and economy.They are widely used in electronic power,communication and other fields.However,a large number of intermetallic compounds,such as Al₂Cu,AlCu and Al₄Cu₉,will be formed during the preparation and use of Al/Cu composites,resulting in a decline in the comprehensive properties of the materials.Therefore,adding a stable interlayer between aluminum and copper to inhibit or reduce the formation of intermetallic compounds is of great significance for the study of Al/Cu composites.In this paper,the method of electroless plating+electroplating is used,that is,electroless plating Ni on the surface of pre-treated Al material,and then electroplating Cu on the Ni-plated material to prepare Al/Ni/Cu composites.By means of SEM,EDS,XRD,microhardness tester and conductivity measuring instrument,the properties of electroless Ni interlayer with different components and the effects of heat treatment temperature and time on the microstructures,interfacial diffusion,mechanical and electrical properties of the composites were studied.Copper electroplating was carried out in 220g/L CuSO₄·5H₂O,60g/L H₂SO₄,0.2mL/L HCl solution.The cathode current density was 6A/dm²,the anode current density was 2A/dm²,and the temperature was 18-35?.The Al/Cu composite without intermediate layer was prepared.The coating was bonded firmly.It was found that the interfacial diffusion layer thickness and surface resistivity of Al/Cu composites increased gradually with the increase of temperature under the same holding time,and the resistivity increased and the trend slowed down with the prolongation of heating time.Electroless Ni-P plating was carried out on the Al matrix prepared by a certain amount of NiSO₄·6H₂O,NaH₂PO₂·H₂O and CH₃COONa dipping solution,and then the Al/Ni-P/Cu composite was prepared by electroplating copper on the surface of the solution.It was found that the content of P in the coating increased with the concentration of reducing agent NaH₂PO₂·H₂O in the dipping solution.The coating changed from crystalline to amorphous,and its hardness increased first and then decreased.No interfacial diffusion occurs below 450?,and solid solutions of Al₃Ni,Al₃Ni₂ and Cu-Ni are formed successively after 450?.The resistivity of Al/Cu composites without interlayer changes little compared with that of Al/Ni composites without interlayer.The results show that the formation of Al-Cu intermetallic compound is inhibited to some extent by the Ni-P interlayer,and the Ni-P intermetallic coating with low P content has stronger inhibiting ability than the Ni-P intermetallic coating with medium and high P content.In the experiment,Ni-B was electroless plated on Al substrate with a certain amount of immersion solution of NiSO₄·6H₂O,KBH₄ and CH₃COONa,and then Cu was electroplated on the surface of Al/Ni-B/Cu composite.It was found that the content of B in the coating increased with the concentration of reducing agent KBH₄ in the dipping solution,and the coating changed from crystalline to amorphous.The hardness of the coating first increased and then decreased.The inhibition of Al/Cu interface diffusion was the same as that of the Ni-P intermediate coating.The resistivity of Al/Cu composites with no intermediate layer has little change,and is lower than that of Ni-P coatings.The results show that the formation of Al-Cu intermetallic compound is inhibited to some extent by the Ni-B interlayer,and the Ni-B intermetallic coating with medium and low B content has stronger inhibiting ability than the Ni-B intermetallic coating with high B content.