Study On The Thermo-Mechanical Treatment Of Copper Based Spot Welding Electrode With Poly-Elements Strengthening

Cu-Cr-Zr-Ni-Si and Cu-Cr-Zr-Co-Si spot welding electrode alloys were prepared by vacuum melting and casting,by means of conductivity test,hardness test,metallographic microscope,SEM,EDS,XRD and TEM,the effects of different alloying elements on the electrical conductivity,mechanical properties and microstructure of the alloy were studied under different thermo mechanical processes.The main results are as follows:1.The cast microstructure of Cu-Cr-Zr-Ni-Si alloy is mainly composed of columnar crystals,and a large amount of coarse surplus-phase is dispersed in the matrix.The cast microstructure of Cu-Cr-Zr-Co-Si alloy is mainly composed of equiaxed grains,and there are a large number of granular precipitates and gray precipitates are dispersed in the matrix.After solution treatment,surplus-phase of Cu-Cr-Zr-Ni-Si alloy is dissolved in the matrix,the gray precipitation in Cu-Cr-Zr-Co-Si alloy is completely dissolved in the matrix,and the granular granular Co5Cr3Si2 phase not dissolved.both the hardness and the conductivity of Cu-Cr-Zr-Ni-Si and Cu-Cr-Zr-Co-Si alloys decrease when compared to the cast state,after the solution treatment.After cold rolling,the grain size of the alloy elongated along the rolling direction.The electrical conductivity of Cu-Cr-Zr-Ni-Si and Cu-Cr-Zr-Co-Si alloy changed little by cold rolling,but the hardness of the alloy increased greatly.2.The hardness and conductivity of the alloy Cu-Cr-Zr-Ni-Si and Cu-Cr-Zr-Co-Si alloy increased rapidly at the beginning of aging.The greater the amount of pre-deformation,the shorter the time of the maximum hardness of the alloy,and the faster the decrease of the hardness of the alloy with the aging time.With the prolongation of the aging time,the increase of the conductivity of the alloy tends to slow down.The precipitation phase of Cu-Cr-Zr-Ni-Si alloy at the aging stage is mainly CrSi2 phase and Ni2Si phase.The precipitation of Cu-Cr-Zr-Co-Si phase is mainly Co5Cr3Si2 phase and Co2Si phase.3.Under the same amount of pre-deformation and solution treatment,the m-aximum conductivity of Cu-0.6Cr-0.15Zr-2.8Ni-0.7Si alloy is greater than that of Cu-0.6Cr-0.15Zr-2.8Ni-0.9Si alloy,and the maximum conductivity of Cu-0.8Cr-0.15Zr-3.5Co-0.7Si alloy is higher than that of Cu-0.8Cr-0.15Zr-3.2Co-0.8Si alloy.T-he maximum hardness of Cu-0.6Cr-0.15Zr-2.8Ni-0.9Si alloy without cold rolling and different pre-deformation is greater than that of Cu-0.6Cr-0.15Zr-2.8Ni-0.7Si alloy.The maximum hardness of Cu-0.8Cr-0.15Zr-3.5Co-0.7Si alloy with pre-def-ormation of 20%and 40%is higher than that of Cu-0.8Cr-0.15Zr-3.2Co-0.8Si al-loy.The maximum hardness of Cu-0.8Cr-0.15Zr-3.2Co-0.8Si alloy with pre-defor mation of 60%and 80%is higher than that of Cu-0.8Cr-0.15Zr-3.5Co-0.7Si alloy.The softening temperature of Cu-0.8Cr-0.15Zr-3.2Co-0.8Si alloy with a pre-defor mation of 60%Cu-0.6Cr-0.15Zr-2.8Ni-0.9Si is 434?,and the pre-deformation is80%.The softening temperature of the alloy is 645?.4.The Avrami phase transition kinetics equation and Avrami electrical condu ctivity equation of Cu-0.6Cr-0.15Zr-2.8Ni-0.9Si alloy with pre-deformation of 60%at aging temperature of 550?are as follows:f=1-exp(-0.0108t^1.03649)ands=15.9+27.3^{[1-exp?-0.1937t0.48218?]}.The Avrami phase transition kinetics equation and electrical conductivity equation of Cu-0.8Cr-0.15Zr-3.2Ni-0.8Si alloy with pre d e f o r m a t i o n o f 8 0%a t a g i n g t e m p e r a t u r e o f 4 5 0?a r e a s f o l l o w s:f=1-exp(-0.0108t^1.03649)ands=20.15+33.55^{[1-exp?-0.0108t1.03649?]}.