Structures And Properties Of Cu-Y₂O₃Composites Prepared By Liquid Phase In-situ Reaction

Oxide dispersion strengthened (ODS) copper matrix composites are particularly attractive for their excellent combination of electrical conductivity, strength and heat resistance properties, which have been widely used as electrode materials, contact materials, integrated circuit lead frame materials and so on. In this paper, Gu-Y2O3composites were prepared by liquid phase in-situ reaction. Liquid phase in-situ reaction, a new preparation method of ODS composites, with which the solute atoms are in-situ oxygenated to oxide particles at molten state, through heats the alloys up to the liquid phase line temperature. The distribution state of rare earth elements yttrium in copper and their effects on the microstructures and properties have been studied. The microstructures and properties of Gu-Y2O3composites, and the in-situ oxidation mechanism of the Y2O3particles have also been investigated emphatically. The results show as follows:1. The rare earth is a very effective additive in metallurgy industry. The molten copper metal can be decontaminated and the grains in the structure as-cast are refined by adding rare earth elements yttrium, impurity elements such as O, S, P, are reduced obviously. The electrical conductivity of copper would be improved by adding a little elements yttrium, the maximum value of electrical conductivity appears when the content of yttrium is0.05%, which is102%IACS. The microhardness of Cu-Y alloys increases as the content of yttrium increases, the microhardness is72HV when the content of yttrium is0.4%.2. The solubility of yttrium in copper matrix is less than0.04%. The surplus yttrium atoms exist with the form of centre compound, which likes to gather at the grain boundary. The XRD results indicate that the centre alloy phase at copper-rich end of the Cu-Y phase diagram is Cu7Y.3. The Cu-Y2O3composites were prepared by liquid phase in-situ reaction, the volume percent of the Y2O3particles is1.7when the weight percent of yttrium is0.4. The TEM results show that the Y2O3particles dispersed in copper matrix uniformly, the size of Y2O3particles is7nm and the distance between Y2O3particles is20nm. Selected area diffraction attern analysis of2O3particles indicated an (422)Y2O3//(111)Cu,(444)Y2O3//(220)Cu, and [011]Y2O3//[112]Cu orientation relationship with copper matrix.4. The Cu-1.7vol.%Y2O3composites has excellent electrical conductivity and good strength, and the electrical conductivity and tensile strength were98%IACS,558MPa, respectively. The effect of the electrical conductivity of composites by cold-rolled was not conspicuous. With a transformation of80%, the microhardness of composites increased from83HV to127HV.5. The interaction between Y2O3particles and moving dislocation belong to Orowan model. According to the quantitative relationship between the yield strength of the composites and the sizes, volume fraction of Y2O3particles, the added values of the yield strength of the composites by Orowan mechanism was400MPa, which demonstrated that Y2O3was attractive as dispersoids for copper alloys.