Research On Preparation And Application Basis Of New Type Cu/Al Composite Wire

Due to the light weight and good electrical conductivity,copper/aluminum composite wire has a wide range of application prospect in the field of aerospace.However,traditional copper/aluminum composite wire is made of pure copper and pure aluminum as the matrix material.The strength of wire is rather low,and pressure welding performance is poor due to the poor elasticity,which severely limits the application range of this composite wire.Based on the pure copper/pure aluminum composite wire,Cu-Ni-Si/Al-Mg-Si composite wire with higher strength and better elasticity has been developed in this paper.The interface,microstructure and fracture of the composite wire were observed by metallographic analysis,scanning electron microscopy,transmission electron microscopy and so on.The mechanical and conductive properties of the composite wire and interface were measured by stretching,repeated bending,nanoindentation and conductivity test.the evolution law of the interface and the performance and the relationship between each other were analyzed and interpretated.The effect of annealing process on the properties of Cu-Ni-Si/Al-Mg-Si composite wire with different diameter was studied.The optimum performance of<D0.5mm composite wire was obtained after annealing at 350°C×0.5h,and the tensile strength is 256.4MPa,elongation is 5.1%,conductivity is 52.1%IACS.Compared with Cu/Al composite wire of the same specifications,the tensile strength increased by more than 100%.Compared with ?1mm Cu-Ni-Si/Al-Mg-Si composite wire,the comprehensive mechanical properties of the composite wire are slightly decreased,indicating that the smaller diameter of the composite wire,the greater effect of the intermetallic compound formed by the interfacial diffusion on the composite wire performance.When the interface layer is thin,the interface layer plays the role of "bridge",connecting the two alloys and transmitting the stress.When the interface layer becomes thick,the interface bonding strength decreases sharply,and the interface is easy to break.Because the hardness of AlCu phase is the highest,the stress concentration is easy formed at the time of stretching,and the interface is easier to crack between Al2Cu phase and AlCu phase or within the AlCu phase.The Cu-Ni-Si/Al-Mg-Si composite wire can be used to replace the pure copper wire.By adjusting the wire diameter,the weight per unit length is reduced by about 28%while the current carrying capacity difference is very small.If the composition design and process optimization are continued,the unit length weight is expected to be reduced by 40%at the same carrying capacity.By studying the interfacial characteristics of the composite wire during the preparation and annealing process,the bonding mechanism of the interface of the composite wire was analyzed.The bonding process of the composite line interface can be divided into four stages:the interfacial mechanical bonding stage,the interfacial interdiffusion stage,intermetallic compound nucleation stage,intermetallic compound diffusion layer growth stage.The effects of different diffusion annealing processes on the interfacial diffusion layer thickness and intermetallic compounds of Cu/Al and Cu-Ni-Si/Al-Mg-Si composite wires were studied.When Cu-Ni-Si/Al-Mg-Si composite wire is annealed at 250?,an intermetallic compound diffusion layer forms at the interface which is Al2Cu phase;when annealed at 300?,two intermetallic compound diffusion layer forms,which are AlCu phase and Al2Cu phase;when annealed at 350??450?,three kinds of intermetallic compound diffusion layers were formed,which are divided into Al4CU9 phase,AlCu phase and Al2Cu phase;when annealed at 500?,four intermetallic compounds were formed at the interface,which are Al4CU9 phase,Al2CU3 phase,AlCu phase and Al2Cu phase Respectively.the only difference with Cu/Al interface is that annealed at 300?,Cu/Al interface generated three intermetallic compounds including Al4CU9 phase,AlCu phase and Al2Cu phase.This phenomenon may be caused by the different growth rate.So the alloying elements do not substantially affect the kind of intermetallic compounds at the interface.The hardness and elastic modulus of the intermetallic compound are much higher than that of the matrix material.The hardness of Al4CU9,Al2Cu3 and AlCu is above 10GPa,the hardness of Al2Cu is slightly lower(7.36GPa),but it is much higher than that of Cu and Al(2GPa).The thickness of interface diffusion layer of Cu/Al and Cu-Ni-Si/Al-Mg-Si composite wire increases with the increase of temperature and time.When the total thickness of interface layer is larger than 2.5?m,the elongation of the composite wire begins to decrease.At the same temperature,the diffusion rate of Cu atoms in the A1 matrix is greater than that of the A1 atoms in the Cu matrix,resulting in the Kirkendall effect,and leading to the Kirkendall holes appear at Cu/Al interface.The mechanism of Cu/Al diffusion is the vacancy mechanism.In the interface of Cu-Ni-Si/Al-Mg-Si composite wire,the Ni and Si elements migrate to the vacancy space,which effectively hinders the vacancy defects and hinders the generation of Kirkendall holes.The intermetallic compounds formed at the interface of Cu/Al and Cu-Ni-Si/Al-Mg-Si composite wires were subjected to kinetic analysis.The growth coefficients and growth energies of the diffusion layers at different temperatures were obtained.The diffusion dynamics models of interface were established.The influence of alloying elements on the interfacial diffusion of copper and aluminum was analyzed by comparing the two interfaces.The alloying element improves the recrystallization temperature of the copper matrix,and the grain boundary diffusion is less than that of the Cu/Al interface,which reduces the diffusion rate of A1 into Cu.At high temperature,the Cu grain grows in Cu/Al,and the number of grain boundaries decreases,and the physical barrier effect of Kirkendall hole is obvious.Ni and Si elements on Cu-Ni-Si/Al-Mg-Si interface fill this physical barrier,so that the interface diffusion rate exceeds the Cu/Al interface.The effect of cold drawing on the interface after annealing at different temperatures was studied.The brittle and hard intermetallic compounds were difficult to deform during the drawing process.The stress concentration led to the cracking of the Cu-Ni-Si layer.Due to the formation of intermetallic compounds,elongation can not accurately reflect the plastic deformation performance of the composite wire.