| In recent years,with the rapid development of modern industry and technology,many fields such as aerospace,machinery manufacturing and microelectronics has put forward higher requirements on the performance of copper alloys.The strength is generally greater than 600 MPa and the conductivity is greater than 80%IACS.However,copper has a poor strength despite its high electrical conductivity.So how to improve the tensile strengthe as far as possible on the premise of high conductivity of copper has been a hot topic.In this paper,the nano scaled copper alloys with high strength and high conductivity were prepared by mechanical alloying and rapid hot pressing sintering at low temperature.Then a series of unreported high performance Cu-Fe,Cu-Fe-Cr,Cu-Fe-Zr and Cu-Fe-P alloys were prepared by adding some alloying elements.The combination of fine grain strengthening and microalloying strengthening ensures that the strength of copper can be improved significantly with a little damage to its electrical conductivity.The influence of preparing conditions of nano powders and sintering process of nano blocks on the properties of the alloys were studied.And then the elements distribution,enhancement mechanism and microstructures were also studied.The results showed that:1.Mechanical alloying combined with rapid hot pressing at low temperature is an effective way to prepare nano structured Cu-Fe,Cu-Fe-Cr,Cu-Fe-Zr and Cu-Fe-P alloys.2.Nanometer copper powders with high activity were successfully prepared from pure copper powder by high energy ball grinding.Then nanostructured Cu-Fe alloys were prepared by sintering the nano copper powders with pressure at low temperature.The Cu-Fe alloy showed a high tensile strength of 649 MPa and electrical conductivity of 71.86%IACS.The main strengthening mechanism is nano-enhancement.3.The preparation process of nanometer copper alloy powders with high activity was described in detail.And the factors of introducing iron and other impurities in the process of ball grinding were analyzed.The addition of trace alloying element such as Cr,Zr and P can reduce the iron content contaminated in the process of ball grinding,affect the efficiency of ball grinding and reduce the degree of powders agglogeration.So they promote the sintering densification and affect the alloys' properties.Among them,the tensile strength of Cu-Fe alloy is the best which is up to 771 MPa.With the addition of Cr,Zr and P,the strength of Cu-Fe alloy decreases while the conductivity is improved.But compared with Cr and Zr,the Cu-Fe alloy has a significant increase in electrical conductivity and a smaller reduction in strength with the less addition of P.4.With 0?0.5 wt.%Cr addition,Cu-Fe-Cr alloys were prepared successfully.The influence of Cr content on grain size,iron content,microstructure and properties of the Cu-Fe alloys were discussed.The addition of 0.2 wt.%Cr refined the grain,reduced the iron content,purified the matrix structure and improved the conductivity of the alloy.Its optimal comprehensive performance is conductivity of 73.37%IACS,and strength of 513 MPa.5.With 0?0.5 wt.%Zr addition,Cu-Fe-Zr alloys were prepared successfully.The influence of Zr content on grain size,iron content,microstructure and properties of the Cu-Fe alloys were discussed.The addition of 0.1 wt.%Zr reduced the iron content,purified the matrix structure and improved the conductivity of the alloy.Its optimal comprehensive performance is conductivity of 75.19%IACS,and strength of 502 MPa.6.With 0?0.04 wt.%P addition,Cu-Fe-P alloys were prepared successfully.The influence of P content on grain size,iron content,microstructure and properties of the Cu-Fe alloys were discussed.The addition of 0.025 wt.%Zr reduced the iron content,purified the matrix structure and improved the conductivity of the alloy.Its optimal comprehensive performance is conductivity of 80.41%IACS,and strength of 517 MPa. |
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