Preparation And Properties Of Copper-based Functional Gradient Materials

Based on the performance requirements of electrical contact materials, a newcopper-based functionally gradient materials were prepared, in which the high wear-resistant surface layer was formed, and the base material still had good electricalconductivity and mechanical properties. The TiB2have been studied extensively becauseof its good properties, such as high strength, wear resistance, high melting point, goodelectrical conductivity and so on. The rare earth oxide Gd2O3could refine microstructureof composites, and improve the mechanical and anti-arc erosion properties. They wereideal for copper-based reinforcement of functionally gradient materials.In this paper, copper-based functionally gradient materials were fabricated byvacuum hot pressing sintering. The materials were comprised of TiB2/Cu as gradientsurface and Gd2O3/Cu for the ground layer. This study mainly focused on the effects of hotpress parameters and mechanical properties of the gradient materials. Combinedmetallographic (OM) with X-ray diffraction (XRD), scanning electron microscopy (SEM),high resolution transmission electron microscopy (HRTEM) and other analytical methods,the microstructure of gradient material and interface bonding situation were analyzed.The results indicated that the graded materials which obtained at sinteringtemperature of900oC, holding time of30min and sintering pressure of30MPademonstrated the superior properties. With the increasing of reinforcing phase TiB2、Gd2O3content, the conductivity of each graded layer composites were decreased. Whenthe TiB2content reached3wt.%, the conductivity of TiB2/Cu composites still remained at62.0%IACS and while the Gd2O3content reached4wt.%, the conductivity of compositeswas84.0%IACS, which could meet the requirements of high conductivity. The test resultsof mechanical properties showed that within the range of TiB2content from1wt.%to3wt.%, the tensile strength and flexural strength of gradient materials was increased firstand then gradually decreased with increasing of TiB2content. When the TiB2content was2wt.%, the strength of gradient materials reached a maximum, and the gradient tensilestrength was270MPa and flexural strength was680MPa. Though the TiB2content was different, the tensile strength of gradient materials were between the correspondinghomogeneous materials, and the T-G bending strength were all greater than the G-Tbending flexural strength.The analysis of microstructure revealed that in the TiB2/Cu gradient layer, theinterface bonding state between TiB2and Cu was modified by electroless copper plating,which played an important role in enhancing load-bearing body. And in the range ofsintering temperature, a chemical reaction happened between Gd2O3and the copper matrix,and a new phase Gd2CuO4was formed in the Gd2O3/Cu graded layer. It was beneficial toimproving the mechanical propertity of materials. In addition, the interface between twograded layers was disappeared, which could maintain a good continuity in the gradientmaterials.