| Cu-Ag alloy is a promising conductor with high mechanical strength,which has attracted the attention of domestic and foreign scholars due to its excellent composite properties and simple preparation process.It is widely used in transportation,machinery manufacturing,aerospace and other fields,especially for unconventional environmental media,Cu-Ag alloy plays an important role in the application of non-destructive high strength magnets.The field winding coil is the main structural component in the high pulse magnetic field.In order to load the strong excitation current,the winding coil should have high mechanical strength and electrical conductivity.Cu-Nb alloy and Cu-Ag alloy as fiber composites are considered to be the most promising materials.The microstructure of Cu-Ag alloy determines its mechanical and electrical properties.As the microstructure is directly affected by heat treatment and mechanical treatment,the properties can be adjusted by optimizing the preparation process.In this paper,Cu-5.8%Ag-0.6%Nb combined with cold deformation and heat treatment were studied,the microstructure of the alloy was regulated,and the influence of the preparation process on the precipitation phase of Ag and the comprehensive properties of the alloy was mastered.DSC curves of Cu-5.8%Ag-0.6%Nb solution gold were tested at different heating rates.The results indicated that the activation energy was 85.6±6.7KJ/mol when the reaction temperature was 350℃～450℃.Cu-5.8%Ag-0.6%Nb alloy was treated by isochronous heat treatment.The results show that Nb phase is distributed at grain boundary as spherical particles in the alloy.At low temperature,Ag precipitates only exist in discontinuous precipitates,which are preferentially precipitated at grain boundaries with higher energy and around Nb particles.At high temperature,Ag precipitates have both discontinuous and continuous precipitates.With the increase of temperature,the size and spacing of Ag precipitates increased.However,when the temperature was too high,Ag precipitated phase spheroidized and discontinuous Ag precipitated phase spheroidized obviously.The discontinuous Ag phase and the smaller continuous Ag phase were precipitated in the alloy tissues treated with 450℃ for 2 hours,achieving a maximum strength of 269MPa,hardness of 97HV and conductivity of 75%IACS.The results showed that the microstructure of Cu-5.8%Ag-0.6%Nb alloy was fibrous,and the eutectic phase and as-cast Ag precipitated phase were deformed along the rolling direction.The effects of various factors on microstructure and conductivity of the alloy were analyzed.The results showed that the eutectic phase and Ag precipitated phase of the alloy were spheroidized to some extent after annealing,and the Ag precipitated phase presented large spherical particles and some dispersed fine particles.Moreover,diffraction peaks(111),(200)and(220)of Ag phase appeared,and the intensity of diffraction peaks gradually increased with the increase of variables.Among them,the effect of heat treatment temperature is the most significant,while the effect of magnetic field strength is not significant.The grain orientation distribution,degree of recrystallization,grain boundary type and texture of rolled-annealed alloy were analyzed.The results indicate that it is the alloy with a degree of recrystallization with 22%recrystallization grains and 8%sub-crystal grains after annealing at 400℃/2h/25T.There are a lot of small Angle grain boundaries in the alloy to show the substructure inside the grain.Rolling of the alloy after annealing still exist certain preferred orientation,form,texture,in ODF diagrams(D2=40°～5° in texture.It is annealed alloys with the best overall mechanical properties at 400℃/4h/25T with a strength of 671 MPa and conductivity of 74%IACS. |
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