| Cu-Ag alloy are considered to be one of the most promising materials,which have attracted the attention of researchers due to its high conductivity and strength performance.It is widely used in large-scale integrated circuit lead frames,strong magnetic field magnet systems,and large high-speed turbine generator rotor wire and contact wire for high-speed train in the future.The microstructure of a material determines its mechanical and electrical properties.The microstructure of Cu-Ag alloy is directly affected by solidification structure,heat treatment system and mechanical treatment.Therefore,the properties can be improved by controlling solidification structure,improving heat treatment system and optimizing deformation process.In this paper,the effect of adding Nb and Cr elements on the solidification structure of Cu-Ag alloy was studied,and the effect of electromagnetic stirring on the solidification structure of Cu-Ag alloy large size ingots was studied.Cu-Ag alloy wires were prepared by deformation processing and heat treatment.The as-cast structure of Cu-6%Ag alloy consists of primary Cu phase and dispersed divorced eutectic.Nb elements in Cu-6%Ag-1%Nb alloy are mainly dispersed in the vicinity of eutectic tissue in the form of nanoparticles,while Cr elements in Cu-6%Ag-1%Cr alloy are mainly dispersed in the eutectic tissue in the form of particles.The addition of Nb and Cr elements reduces the content of Ag in Cu matrix,and correspondingly increases the proportion of eutectic Ag phase,which can refine and elongate the shape of eutectic Ag phase.With the increase of deformation,the conductivity of Cu-6%Ag alloy decreases gradually,while the hardness and strength increase.The intermediate heat treatment can slightly improve the conductivity.After the addition of the third element,the conductivity of Cu-6%Ag-1%Nb alloy and Cu-6%Ag-1%Cr alloy was slightly lower than that of Cu-6%Ag alloy,but the strength and hardness were significantly improved,among which the addition of Cr element had the most obvious effect on the strength of the alloy.When deformation ?=5.28,the ultimate tensile strength of Cu-6%Ag-1%Cr was increased by 23%and the conductivity decreased by only 6%compared with Cu-6%Ag alloy.The as-cast structure of cu-18%Ag alloy is composed of mesh-eutectic structure of primary cu-rich phase and dendrite gap.Nb and Cr elements in the third group also exist in the form of particles,among which Nb particles are small in size and both of them are scattered near the eutectic structure of cu-ag structure.After adding Nb and Cr elements,the thickness of eutectic tissue decreased and the Ag content in Cu matrix decreased.With the increase of deformation,the strength and hardness of the alloy can be significantly improved by adding Nb and Cr elements while the conductivity decreases less,among which Cr element has a better effect on the improvement of mechanical properties.When the deformation rate ?=5.28,the conductivity of Cu-18%Ag alloy decreased by 8%compared with Cu-18%Ag-1%Cr alloy,and the ultimate tensile strength increased by 21%.Electromagnetic stirring can refine the grain structure of Cu-6%Ag alloy ingot and make the grain size distribution more uniform.At the same time,electromagnetic stirring can refine eutectic structure and make it more slender.The average thickness of eutectic structure decreases by 55.30%.The strength and hardness of Cu-6%Ag alloy under electromagnetic stirring were higher than those without electromagnetic stirring.However,due to the slight loss of Ag content in smelting,the mechanical properties of wires with or without electromagnetic stirring alloy after large deformation were close to each other.With the increase of deformation degree,the conductivity of Cu-6%Ag alloy decreases,and the conductivity of the alloy without electromagnetic stirring is higher than that of the alloy without electromagnetic stirring. |
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