Cu-Cr Mechanical Alloying And Microstructures And Propertiesof C/(Cu-Cr) Composites

Graphite/copper matrix composites,novel kind of advanced material, are considered to have great potential application due to its combinations of excellent conductivity, thermal conductivity, good erosion resistance to electricity arc as well as excellent wear resistance and are broadly used as the electric contacts and brush materials. While the interface between the carbon and the copper matrix exists in the form of mechanical bonding in composites manufactured by powder metallurgy method, which has the low bonding strength and often has a serious impact on the performance of Graphite/copper matrix composite materials, the improvement of strength, hardness and wear resistance has become a important problem for the research and development of graphite/copper composite materials.Research has found that the contact angle between copper and graphite can be reduced by chromium and that copper-chromium alloy often has a higher strength than copper. Therefore in this paper we use mechanical alloying technology to pre- pare Cu-Cr supersaturated solid solution alloy powder by optimizing component design. The powder metallurgy method is also used to manufacture C/(Cu-Cr) com- posites. All of these work aims at developing high-performance copper matrix self-lubricating composite materials and lays a technique foundation for the develo- pment of novel composites. The work includes the following aspects:(1) In this paper mechanical alloying method was used to prepare Cu-5wt%Cr alloy powder. The XRD was adopted to analyze the mechanical alloying process of Cu-5wt%Cr.The result shows that: with the increase of ball-milling time, the particle and grain of Cu-5wt%Cr powder refine gradually, the X-ray diffraction peaks of both copper and chromium become broader and their intensity decrease. Cu-Cr super saturation solid solution was obtained by 60h milling.(2) Powder metallurgy method was used to manufacture C/(Cu-Cr) composites and the influence of manufacture process on the properties of copper matrix graphite composites is discussed. The results showed that: In the process of repression, with the content of Cu-5wt% Cr composite powders in the composite material increasing, the difficulty of cold repression is increasing. Annealing treatment at 400℃before repression can effectively alleviate the difficulty. To ensure the density of materials, the suppress force must be increased at the same time.Thus the prepared C / (Cu-Cr) composite materials have a high density and the strengthening effect of Cu-5wt% Cr composite powders can be preserved.(3) In this paper the influence of matrix-alloying on the properties of graphite /copper matrix composites was studied in this paper. The results show that with the content of Cr increasing, the hardness of graphite/copper composites improves and flexural strength increases first and then decreases, while the conductive performance reduces. The reason is that: At cold repression process, with the content of Cu-5wt% Cr composite powders increasing, it is difficult to achieve higher density of composite and so the bending strength and electrical conductivity are lost.But When the content of Cr in the composite material is less than 1%, the composite powder can effectively strengthen the matrix, only causing a small resistivity increasing.(4) The impacts of Cu-Cr mechanical alloying on the friction and wear performance of C / (Cu-Cr) composite materials are discussed. The results show that: With the increasing of Cr content, the friction coefficient of composite materials increase; when the content of Cr in composite materials is less than 2.0%, the composite material has higher strength and a suitable hardness and a good composite solid lubricating film can be formed, which can effectively reduce the amount of wear and tear. Especially when the content of Cr is 1.0%, the composite materials have the best friction and wear properties; When the content of Cr is more than 2.0%, the strength of composite material reduces and the hardness increases, Abrasive wear is the main wear mechanism. And the higher content of Cr, the greater wear volume.