【作者】 张钦钊；

【导师】 李强；

【作者基本信息】 福州大学 ， 材料物理与化学， 2005， 硕士

【摘要】 本文研究了石墨粒度及其表面化学镀铜对经粉末冶金法制备的铜-石墨复合材料的微观组织结构、物理性能、力学性能的影响,讨论分析了不同摩擦取向 (摩擦取向 A 表示摩擦面垂直于压制方向,滑动方向平行于石墨片平面;取向 B 表示摩擦面平行于压制方向,而滑动方向垂直于石墨片平面;取向 C 表示摩擦面平行于压制方向,滑动方向平行于石墨片的长度方向。) 下的摩擦磨损性能。以铜粉和不同粒度的镀覆、未镀覆石墨粉为原料,经 400MPa 压制成型、950℃×2h 烧结、600MPa 复压制备的石墨含量为 10wt.%的铜-未镀铜石墨、铜-镀铜石墨复合材料的微观组织均匀,密度大于 6.61g/cm3,相对密度高达 98.4%。随石墨粒度的增大,铜-石墨复合材料的微观组织中铜基体从断续分布向连续网状结构变化,石墨片倾向于沿垂直于压制方向排列,垂直和平行于材料压制方向两截面的微观组织结构差异变大。铜-未镀铜石墨复合材料压坯烧结时均发生膨胀,复压后烧结坯体的密度均提高。随石墨粒度增大,压坯密度略有下降,复压后密度则增高,材料的电导率逐渐提高,抗弯强度略有增加。石墨经化学镀铜后,改善材料的组织均匀性和烧结特性,增强铜与石墨间的界面结合力,降低材料的孔隙度,提高材料的密度和抗弯强度,有利于连续铜基体三维导电网络的形成,提高材料的电导率。在给定摩擦试验条件下,不同石墨粒度的铜-未镀铜石墨复合材料在三种摩擦取向下摩擦系数较低,摩擦稳定性好,材料的磨损失重与滑动摩擦距离近似呈线性关系。随石墨粒度的增大,材料的摩擦系数略有增高,磨损率下降,耐磨性提高。石墨表面化学镀铜后,材料的磨损速率显著下降,但小粒度 (1μm、6μm、10μm、25μm) 材料的摩擦系数升高且波动性变大。铜-石墨复合材料在不同摩擦取向下的摩擦磨损性能存在差异,摩擦取向 A 的摩擦系数和磨损率均低于 B、C 取向。磨损表面形貌特征主要由凹坑、犁沟和空洞构成。材料在滑动摩擦中的磨损包括粘着磨损、磨粒磨损、剥层磨损和氧化磨损等形式。随石墨粒度增大,磨损机制从磨粒磨损为主向剥层磨损为主变化。石墨化学镀铜后,趋向于剥层磨损。更多还原

【Abstract】 Copper-graphite composites were prepared by powder metallurgy process.The effect of graphite particle size on the microstructure, physical andmechanical properties of the composites made with copper-coated anduncoated graphite powders via electroless copper plating was investigated.The friction and wear properties were analyzed under the conditions ofdifferent combinations between friction surface, sliding direction and flakegraphite base. The combinations fall into three types, respectively A, B and C.Type A means the combination of friction surface perpendicular to press axisand sliding direction parallel to the flake graphite base, type B means thecombination of friction surface parallel to press axis and sliding directionperpendicular to the flake graphite base, type C means the combination offriction surface parallel to press axis and sliding direction parallel to thelongitudinal direction of graphite flake.Both copper-graphite and copper-copper coated graphite composites withgraphite contents of 10wt.% were prepared by pressing at 400MPa, sinteringat 950℃×2h and repressing at 600MPa. The composites have homogenousmicrostructure, a minimum density of 6.61g/cm3 and the relative density up to98.4%. The particle size of graphite has significant effect on the properties ofthe copper-graphite composites. With the particle size of graphite increased,the netlike copper matrix changes from discontinuous to continuous-skeleton,the orientation of flake graphite base tend to be perpendicular array relative topress axis, the microstructure difference of the composites intersectioned atperpendicular and parallel direction relative to press axis is more remarkable.Volume expansion of the copper-graphite composite greens occurred during<WP=4>石墨粒度及其表面化学镀铜对铜-石墨复合材料性能的影响sintering. The density of the sintered composites was increased afterrepressing. With the graphite particle size increased, the density, the electricalconductivity and the bending strength of the repressed composites increased,but the density of the greens decreased. The graphite powders coated byelectroless copper plating resulted in the uniform graphite distribution in thecomposites, the improvement of sintering, and the enhancement of interfacecohesion between copper and graphite, thus the decrease of the porosity andthe raise of the electrical conductivity and the bending strength of thecomposites.Dry sliding friction and wear tests were performed in a pin-on-ring modeusing three kinds of orientation combinations. It was found that thecopper-graphite composites have lower friction coefficient and better frictionstability, and wear weight losses increase linearly with an increase of slidingdistance. The copper-graphite composites with large graphite particle haveslightly higher friction coefficients but lower wear rates than that with smallgraphite particle. The wear rates of copper-copper coated graphite compositesare decreased obviously with respect to copper-graphite composites. However,the friction coefficients and fluctuation of copper-coated composites withsmall (1μm、6μm、10μm、25μm) graphite particle were increased. Thefriction coefficients and wear rates of the copper-graphite composites in typeA combination are lower than that in type B or C combination. Themorphology characteristics on the worn surface can be divided into three maintypes such as scallop, furrow and cavity. The wear mechanisms of bothcopper-graphite and copper-copper coated graphite composites includeadhesion, abrasion, delamination and oxidation. With the particle size ofgraphite increased, the dominant wear mechanism of the copper-graphitecomposites changes from abrasion to delamination. The wear mechanism ofthe copper-copper coated graphite composites tend to bedelamination-dominant.更多还原