【作者】 张萍；

【导师】 王文芳； 吴玉程；

【作者基本信息】 合肥工业大学 ， 材料学， 2009， 硕士

【摘要】 石墨/铜复合材料,不仅导电性与导热性优异,而且具有良好的抗电弧侵蚀和抗磨损能力以及较高的强度,是一种具有广泛应用前景的新型材料,尤其是在电接触材料领域得到广泛的应用。石墨与铜完全不浸润,在使用粉末冶金方法制备的复合材料当中,两者也只是机械互锁结合,其界面强度低,严重影响了复合材料的性能。因此,如何在保持较高电导率水平的前提下,大幅度地提高强度、硬度和耐磨性的问题已成为铜基复合材料研究与开发的重要问题。有研究发现,铬可减小铜和石墨的润湿角,并且铜铬合金往往具有较高强度,因此本文通过组分优化设计,采用机械合金化技术制备Cu-Cr过饱和固溶体合金粉末,并结合粉末冶金方法制备采用基体合金化方法强化基体的石墨/铜-铬复合材料,以开发高性能铜基自润滑复合材料为目标,为拓展新型铜基复合材料的应用领域提供技术保障。本文的研究主要包括以下几个方面的内容:(1)采用机械合金化技术制备了Cu-5wt%Cr复合粉体,利用XRD分析了Cu-5wt%Cr复合粉体机械合金化过程。结果表明:随着球磨时间的增加,晶粒不断细化,Cu-5wt%Cr复合粉末衍射峰不断宽化,衍射强度逐渐下降;当球磨60h时,Cr已完全固溶在Cu晶格中。(2)采用粉末冶金方法制备了石墨/铜复合材料,探讨了制备工艺对复合材料致密性的影响。结果表明:在复合材料压制过程中,随着Cu-5wt%Cr复合粉体含量的增加,冷压难度增大。压制前对Cu-5wt%Cr复合粉体进行400℃退火处理可部分降低冷压难度,要保证材料的密度,同时还需在一定的范围内增加压制压力,由此制备出的石墨/铜-铬复合材料具有较高的密度,Cu-5%wtCr复合粉末的强化效果能得以保留。(3)分析了基体合金化对石墨/铜复合材料性能的影响,结果表明:随着Cr含量增多,石墨/铜复合材料硬度提高,抗弯强度先增大后减小,导电性能下降。其原因是在冷压工艺下,随着Cu-5wt%Cr复合粉末含量的增加,复合材料难以达到较高密度,从而造成抗弯强度和导电性的损失。当复合材料中Cr含量小于1%时,复合粉末则能有效地增强基体,而使得电阻率只有小幅度的增加。(4)探讨了基体合金化对(7.5%)C/Cu-Cr复合材料摩擦磨损性能的影响。结果表明:随着Cr含量的增加,复合材料摩擦系数增加;当基体中Cr含量小于2.0%时,复合材料具有较高的强度和合适的硬度,摩擦副之间能够形成良好的复合固体润滑膜,有效地降低了磨损量,特别是当Cr含量为1.0%时,复合材料耐磨性最好;当Cr含量超过2.0%时,复合材料强度降低,硬度增加,磨损机制以磨粒磨损为主,Cr含量愈高,磨损量愈大。更多还原

【Abstract】 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.更多还原