Research On Microstructure And Properties Of Cu-Cr-Zr-Co-Si Resistance Welding Electrode Alloy

In this paper,a small amount of Co,Si and Y elements were added to the Cu-0.8Cr-0.15 Zr alloy under the traditional spot welding electrode preparation process,and the comprehensive performance of the copper alloy electrode was improved by the multi-composite strengthening method.Systematically studies the impacts of the alloying elements(Co,Si,Y),the content of alloying elements(Co,Si),the ratio of alloy elements(Co/Si)and the multi-stage aging treatment on microstructure and properties of Cu-Cr-Zr-Co-Si alloy,by means of metallographic microscope,scanning electron microscope,energy spectrometer test method and X-ray diffractometer.The main results are as follows:1.After adding Co,Si and Y elements,the grain refinement of the alloy and the as-cast microstructure is fine equiaxed grains,a large amount of Co5Cr3Si2 phase and a precipitated phase of Co,Si are formed in the matrix,and the precipitates are obviously segregated.After the solution treatment,the gray precipitates phase were completely dissolved in the matrix,but the Co5Cr3Si2 phase did not dissolve and grow up.With the rise of solution temperature,the conductivity of the alloy decreased,the hardness increased.2.In the stage of aging,fine precipitated particles appeared at the grain boundaries and in the grain interior.With the extension of aging time,the precipitated particles gradually increased,and the Co5Cr3Si2 phase gradually became coarsened.At the end of aging period,no Cr element detected in the alloy matrix,and new compounds composed of Co,Zr,Cr,and Si elements appeared.The precipitates are mainly Co5Cr3Si2 phase,Co2 Si phase and CoZrCrSi phase.At beginning of the aging,the conductivity rise rapidly,and the latter upward trend slowed down to maintain stability.The higher the aging temperature,the shorter the conductivity reaches the peak value.The hardness of each alloy reaches the peak value at 450? or 500?aging,and the hardness of the alloy decreased rapidly in the 550? and later period of aging at 500?.3.After the aging treatment,adding Co and Si elements,the conductivity decreased 35-40%IACS;the hardness increased 30-48HV;adding rare earth elements Y,alloy conductivity increased by 2-3.5%IACS,the hardness increased slightly in4-30HV;after adding alloy elements,the mechanical properties of the alloys were enhanced at high temperature,the high temperature softening resistance of alloy was improved obviously,and the softening temperature was up to 686?.4.As the ratio of Co/Si increases,the hardness and conductivity of the alloy has always maintained:(Co/Si=5)>(Co/Si=4)>(Co/Si=3).The ratio of the elements has a great influence on the peak hardness and conductivity of the alloy,respectively15-40 HV and 6.1-18.3%IACS.With the increase of Co element content in the alloy,the high-temperature softening performance of the alloy decreases.5.When the ratio of Co/Si=4:1 unchanged,with the content of Co,Si element is increased,the alloy conductivity gradually decreased,the hardness value increased.The effect of alloying elements content on the peak value of conductivity is not significant,in 1-5%IACS,the effect of alloy on the peak hardness is limited,only6-10 HV.And with the increase of alloying elements,the high-temperature softening performance of the alloy decreases.6.After pre-aging treatment at 200?x2h,the microstructures of the alloys changed little,and the conductivity and hardness of the alloys were slightly higher than that of solution.The alloy size uniformity,grain coarsening,precipitation of particles increased,and peak value of conductivity and hardness of the alloy increased by 3.5%IACS and 8.3HV,after solution+200?x2h pre-aging+aging treatment.But the high-temperature softening performance of the alloy decreased.