Study On Structure And Properties Of Cu-Cr-Zr Alloy Melted In Non-vacuum Condition

As a kind of typical aging strengthen alloy, Cu-Cr-Zr alloy was widely used in electronic information technology and high-speed electrical railway because of its excellent strength and electrical conductivity. However, its preparation in factory usally adopted vacuum smelting and casting method, which need high technical requirement and production cost. Therefore, study on the structure and properties of Cu-Cr-Zr alloy melted in non-vacuum condition has great and far-reaching significance.In this paper, the structure and properties of the Cu-0.92Cr-0.068Zr, Cu-0.90Cr-0.18Zr and Cu-0.94Cr-0.34Zr alloys melted in non-vacuum condition were studied by metallogrphic micro-analysis, TEM, XRD, tensile test and thermal simulating test. The effects of Zr on the structure and properties of the Cu-Cr-Zr alloy was analyzed.The results showed that the microstructure of the Cu-Cr-Zr alloy melted in non-vacuum condition was coarse columnar grain, and the main composition of the alloy were composed by fine copper matrix, simple substance Cr and intermediate compound Cu-Zr. It can be found that the grains of the Cu-0.90Cr-0.18Zr and Cu-0.94Cr-0.34Zr alloy were bigger than the Cu-0.92Cr-0.068Zr alloy, it indicated that the addition of Zr could refining grains of the Cu-Cr-Zr alloy, but there was no further refining effections with excessive addition of Zr. The electrical conductivity, strength and handness of the casting Cu-Cr-Zr alloy can not meet the production requirement, the average value of the electrical conductivity, strength and handness at room temperature were 51%IACS, 46%IACS, 41%IACS; 100HV, 100HV, 102HV and 240MPa, respectively.The combination of cold deformation and aging treatment can significantly improve the strength, handness and electrical conductivity of the Cu-Cr-Zr alloy. For example, the microhardness and electrical conductivity of the alloy were 135HV and 71%IACS respectively when it was solid solution at 950°C for 1h and aged at 500°C for 1h without cold deformation. While with 60% cold deformation before the same treatment, the microhardness and electrical conductivity of the alloy raised to 151HV and 76%IACS, respectively. The influence of aging time on the microhardness and electrical conductivity of the Cu-Cr-Zr alloy melted in non-vacuum condition showed that with the extension of aging time the electrical conductivity increased quickly at the initial period of aging, then the growth changed to slowly. However, the microhardness of the alloy appeared growth at low temperature and growth firstly then reduction at high temperature.The inner grain and near boundary grain of the Cu-Cr-Zr alloy will generate a large number of dislocation and the precipitated phases uniformly distribute and disperse in the copper matrix after cold deformation, and the alloy strength was improved significantly. The strength of the alloy mentioned in this paper goes to 546MPa, 576MPa and 550MPa, and the electrical conductivity of the alloy reach to 70%IACS,76%IACS and 72%IACS respectively after solid solution and aging treatment and meet the performance requirement.The effects of distortion temperature and strain rate on the flow stress of the Cu-0.92Cr-0.068Zr and Cu-0.90Cr-0.18Zr alloy were studied by isothermal compression test. The results indicated that the higher distortion temperature and the lower strain rate were adopted, the lower the relevant flow stress of the Cu-Cr-Zr alloy showed off. The thermal deformation activation energy of the alloys were counted by Arrhenius hyperbolic sine function, and the flow stress equation was established.