Microstructure And Properties Of High Strength And High Conductivity Cu-Ag Alloy

The Cu-Ag alloy with high strength and high conductivity has a wide application prospect in the fields of pulsed high-field magnets and high-speed train track contact line.In this paper,1 % to 6 %(wt.%)Ag contained Cu-1Ag,Cu-2Ag,Cu-3Ag,Cu-4Ag,Cu-5Ag and Cu-6Ag alloys have been smelted by vacuum induction smelting.Then the wire was processed by cold deformation processing combined with heat treatment(solid solution treatment + aging treatment).The effects of cold working strain,Ag content and heat treatment temperature on the properties of the alloys were discussed.The microstructure and properties of Cu-6Ag alloy during cold deformation and the microstructure of Cu-2Ag alloy under the highest strain were mainly analyzed by scanning electron microscopy and transmission electron microscopy.The main results are as follows:1.In the process of cold drawing,the hardness and strength of Cu-6Ag alloy increase with the increase of draw ratio η,and the electrical conductivity gradually decreases with the increase of draw ratio.Non-equilibrium eutectic was found in the microstructure,and the eutectic phase aligned along the drawing direction during drawing,and the thickness was thinned due to drawing.When η = 3.86,the average thickness of eutectic phase is 1.047 μm,and when η = 7.61,the average thickness is refined to 188 nm.The dislocations and refined eutectic fiber phase significantly increase the strength of the alloy,and at the same time increase the electron scattering and decrease the electrical conductivity.2.The higher the Ag content is,the more significant the enhancement of hardness and strength through solid solution strengthening,precipitation strengthening and phase boundary strengthening will be,and the scattering effect on electrons will also be increased.Under the same strain,with the increase of Ag content in Cu-Ag alloy,the alloy exhibits higher hardness and lower electrical conductivity,and the variation trend of strength is basically the same as that of hardness.Deformation twins and stacking faults were found in the microstructure and the distribution of dislocations was not uniform.The WH method was used to calculate the dislocation density of Cu-2Ag at room temperature.It was found that the dislocation density decreased slightly with the increase of deformation,but still maintained at the same order of magnitude.The microstructure and properties of low temperature drawing Cu-2Ag alloy are similar to those of room temperature drawing.The possible reason for the failure to introduce a large number of twins into the Cu-2Ag microstructure is that the actual working temperature may be much higher than the temperature of liquid nitrogen due to the long drawing time under high strain.3.When the annealing temperature is below 300℃,the hardness value of Cu-Ag alloy has no significant change,and the electrical conductivity is improved due to the decrease of the solid solubility.When annealed at 400 ℃,recrystallization may occur,and the hardness and strength of the alloy are greatly reduced,and the electrical conductivity is significantly increased.After annealing at 300℃,the strength,hardness and conductivity of Cu-6Ag alloy are 969 MPa,276 HV and 85.6% IACS,respectively.The strength,hardness and conductivity reach a good combination,and the comprehensive properties are improved.