| The aging strengthened Cu-Ni-Si alloy has excellent conductivity and strength,excellent processing characteristics and no magnetism.It has a good prospect in the application of lead frame materials for integrated circuits.In this paper,four kinds of Cu-3Ni-0.75Si-XSn-0.1Mg alloys with different Sn content were designed on the basis of the brand of C7025 alloy?Cu-Ni-Si-Mg?.The effects of different Sn content on the microstructure and related properties of the alloy were studied.The microstructure evolution and strengthening mechanism of the alloy during deformation and aging treatment were analyzed,and the softening mechanism of the peak aged alloy annealed at different temperatures was explored The results are as follows:The Sn elements were dispersed in the Cu-3Ni-0.75Si-XSn-0.1Mg alloy matrix,which improved the segregation phenomenon of the as-cast structure of the alloy.The addition of Sn can improve the hardness of the alloy,but at the same time reduce the electrical conductivity of the alloy.Through the analysis of the structure,it was found that during the aging process,the nano-scale Ni2Si phase precipitated by the alloy dissolves and strengthend the alloy,and the added Sn element can refine the Ni2Si phase precipitated by aging,thereby improving the precipitation strengthening effect of the alloy and improving the performance of the alloy.The peak aging hardness of the alloy is between 260.9HV-274.7HV,and the conductivity is about 33%IACS.Research on the softening mechanism of the solution-cold-rolling-peak aging Cu-3Ni-0.75Si-XSn-0.1Mg alloy has found that the annealing mechanism at different temperatures has different softening mechanisms:At 450°C,the annealing softening effect of the alloy was caused by recovery;at 500°C-550°C,the softening effect of the alloy was attributed to the combined effect of precipitation phase coarsening,grain growth,recovery and partial recrystallization;at above 600?,the coarsening and recrystallization of the precipitated phase of the alloy structure caused the softening of the alloy.After comparing the stress relaxation properties of alloys with different Sn contents at three different temperatures:room temperature?25°C?,100°C,and 150°C,it was found that the Sn element can improve the stress relaxation performance of Cu-Ni-Si alloys.The precipitation of the second phase of Cu-3Ni-0.75Si-XSn-0.1Mg alloy is the main reason to improve the stress relaxation stability of the material. |
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