| This topic originated from the National Natural Science Foundation funded project:"Interfacial metallurgical behavior of Cu/Al laminates under the influence of rolling stress/strain field" granted number (50964006).Cu-Al composite materials not only have good conductivity, high thermal conductivity and good corrosion resistance of Cu, but also have light weight, wear resistance, and economic advantages of Al. They have been widely used in metallurgy, machinery, automotive, electronics, electricity, electrical appliances and household items and other areas. In the trend of "saving copper with aluminium", using Cu/Al laminates instead of Cu for preparing high-frequency cables illustrates a good prospect of application.In this study, Cu/Al laminates were made by cold roll bonding.The growth law of interfacial diffusion zone was studied when the cold rolling reduction rates of Cu/Al laminates were55.7%,65.6%,76.1%and81.3%. The theoretical kinetics model of the diffusion zone growth under the effect of the strain field produced by rolling was established, It provided theoretical basis for prediction and control of the growing interface diffusion zone. The hot deformation behaviors of cold-rolled Cu/Al laminates under conditions that the temperature is400～500℃and the strain rate is0.0006～0.02s-1were studied. Effects of strain rate, deformation degree and temperature on deformation resistance were analyzed; the constitutive equation of steady flow stress of Cu/Al laminates was established on the basis of test data, they can guide the choice of hot working process parameters of copper/aluminium laminates. It was studied that the interfacial diffusion reaction of cold-rolled Cu/Al laminates under the deformation condition that the temperature was500℃and the reduction rate was0to35%. The generation law of intermediate phases on the Cu/Al interface was analyzed from the aspects of diffusion mechanism, diffusion thermodynamics and kinetics. Effects of reduction on the interfacial diffusion zone growth were also discussed.The results show that:with the increasing of cold rolling reduction rates, the incubation period of interfacial diffusion zone would be reduced and the diffusion coefficient would be increased during the annealing process of Cu/Al laminates. In the high temperature deformation process, the deformation resistance of Cu/Al laminates would be increased with increasing deformation until the dynamic softening balanced with work hardening; it would be maintained at a certain level. When the other deformation conditions were constant, deformation resistance would be reduced significantly with the increasing of deformation temperature; the deformation resistance would be increased with the increasing of strain rate. CuAb, Cu9Al4and CuAl formed on the Cu/Al interface under the deformation condition that the temperature was500℃and the reduction rate was0to35%. In the process of interfacial diffusion and reaction, there existed vacancy diffusion mechanism, surface diffusion mechanism, grain boundary diffusion mechanism and so on. The formation sequence of intermediate phases on the Cu/Al interface depends on both the diffusion kinetic and thermodynamic phase transition. CuAl2and Cu9Al4before CuAl formed on the interface of Cu/Al laminates, which can be related to Gibbs free energy of forming each phase, and follow the principle of flux-energy, the phase which had the thermodynamic maximum driving force of formation formed firstly according to the atomic diffusion flux ratio. The hot pressing reduction rate has a few influences on the Cu/Al interfacial diffusion zone. With the increasing of hot pressing reduction rate, the thickness of Cu/Al interfacial diffusion zone would be increased firstly then reduced, but total volume of the interfacial diffusion zone would be increased gradually. Although the pressure has a few influences on the growing of interfacial diffusion zone, temperature is still the most important factor which affects the Cu/Al interfacial diffusion zone growth. |
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