【作者】 邓景泉；

【导师】 吴玉程；

【作者基本信息】 合肥工业大学 ， 材料学， 2008， 博士

【摘要】 高性能铜基功能复合材料在机械、电子、航空航天等高科技领域有广阔的应用前景。颗粒增强铜基功能复合材料可以具备优良的导电、导热及力学性能,所以研究n-AlN颗粒增强铜基功能复合材料具有重要意义。本文采用高能球磨方法制备铜基n-AlN复合粉体;用粉末冶金方法制备铜基n-AlN功能复合材料。采用SEM,HRTEM,XRD,EDS等手段表征复合材料的组织形貌并测定其力学及物理性能,结果表明:CuCrZr/AlN具有良好的导电、导热及力学性能。本文主要进行了以下几个方面的工作:首先优化球磨工艺,分析了高能球磨过程中Cu-AlN、Cu-Zr-AlN、Cu-Cr-Zr-AlN复合粉体的组织结构、形貌的变化规律;在优化的高能球磨工艺条件下,对于铜氮化铝系复合粉体,获得晶粒细小、尺寸分布均匀的没有合金化的复合粉体;对于铜锆氮化铝系、铜锆铬氮化铝系复合粉体,获得晶粒细小、尺寸分布均匀的合金化的复合粉体。球磨后的复合粉体比表面积增大,晶格畸变增大,处于高内能状态。分析了纳米颗粒在球磨过程中的作用并得出延性与硬脆相复合粉体球磨过程的模型示意图。采用粉末冶金工艺制备铜基纳米氮化铝复合材料。系统研究了压力、烧结温度对致密度的影响,优化了复合粉体的致密化工艺。分析了纳米颗粒、孔隙在致密化中的作用。分析了高能球磨对致密化的影响。用SEM,HRTEM,XRD等手段表征组织形貌,发现粉末与烧结坯组织间有“遗传性”。分析锆、铬元素在复合材料中的作用。铜基纳米复合材料CZCA2(CuCrZr/AlN),在优化的致密化工艺下,材料的抗拉强度为550MPa,抗弯强度401Mpa,软化温度大于700℃。分析了孔隙的属性对力学性能的影响。分析了固溶时效对力学性能的影响及纳米颗粒在热处理过程中的作用。表征了固溶时效过程的组织形貌变化,分析力学性能变化的原因。测定了铜基纳米复合材料的导热系数、导电率。分析了其导热、导电的机理,探讨了纳米颗粒、孔隙对烧结坯体的导热、导电性能的影响。分析了复合材料的导热性能与导电性能之间的关系,计算其洛仑兹值。分析了同溶时效对导热性能、导电性能等的影响,分析了各元素及纳米颗粒在热处理中的行为。选用CZCA2成分,采用工艺:500MPa压制,900℃烧结,后处理为600MPa复压,900℃复烧,制备纳米颗粒强化铜基功能复合材料点焊电极,进行装机实验。结果表明:与商用铸态的Cu-Zr-Cr电极比较,自制电极的寿命提高了20%。用OM、SEM、TEM表征失效的点焊电极的组织形貌,分析了自制电极的失效机制,比较了自制电极与铸态Cu-Cr-Zr电极的组织性能变化。更多还原

【Abstract】 High strength high conductivity copper alloy-based composites are extensively applied in the electromechanical, electronic, atomic energy, etc high-tech fields. It attracts more and more attention from all the countries in the world. Material researchers from all over the world make great efforts on the preparation technology and basic theory of the copper alloy-based composites. Particles reinforced copper alloy-based composites can keep the high electrical and high thermal conductivity of pure copper, and at the same time due to the addition of discontinuous reinforcements the composites can possess an ideal comprehensive properties. In the paper further research was made on nano-particles reinforced copper-based composites. It is expected to develop a new kind of functional materials with high strength, high electrical and high thermal conductivity.Commercial spot welding electrode materials are Cu-Zr, Cu-Cr, Cu-Cr-Zr alloys made by casting. Their electrical conductivity is about 70%IACS, relatively high, but their softening temperature is only 500℃. Their strength is relatively low at high temperature. So in the dissertation Nano- AlN reinforced CuCrZr composites have been fabricated successfully with almost full density, relative density 96.9%, by conventional powder metallurgy, that is, a process of pressing, sintering, re-pressing, re-sintering. It has a good combination of properties of high strength, high thermal and high electrical conductivity. The alloying powders wwere made by way of mechanical milling. The following research aspects have been done.The evolution law of microstructure, particle morphology and mechanical properties has been investigated of the three kinds of powders Cu-AlN, Cu-Zr-AlN, Cu-Cr-Zr-AlN during mechanical milling process. The appreciate preparation conditions for fine, uniform and alloying powders are obtained for milling process, which is beneficial for lowering sintering temperature, shortening sintering time. The function of n-AlN particles is analyzed during milling process.Different composites with different density were prepared using different pressures and different sintering temperatures. In order to improve their density, the technology of re-pressure and re-sintering was used. Composites with almost full density were prepared using the appropriate condition. The function of n-AlN particles is analyzed during densification. The density of the composite Cu-Cr-Zr-AlN is 96.9% by the process of 500MPa pressing, 900℃sintering, then 600MPa re-pressing、900℃re-sintering.Microstructure and morphology of the n-AlN particles reinforced copper composites, with almost full density, were characterized using OM, SEM, TEM, HRTEM, XRD, EDS, HB, HV etc. That the composite structure inherits that of the raw materials was discovered. The composites have uniformly, fine and relatively compacted microstructure. The tensile strength ,the bending strength, the softening temperature of the composites are 600MPa, 401MPa, > 700℃respectively made using the process, 500MPa pressing, 900℃sintering , then 600MPa re-pressing, 900℃re-sintering. The characteristics of the pores’ influence on mechanical properties were analyzed. The influence of solid solution and aging on mechanical properties and the function of Nano-particles were analyzed. The change of microstructure and morphology during heat treatment was characterized and the reason for the change was found.The thermal conductivity and the electrical conductivity of the composites were measured. The thermal conductivity and the electrical conductivity of the composites were 190Wm^-1K^-1, 64% IACS respectively made using the process, 500MPa pressing, 900℃sintering, then 600MPa re-pressing, 900℃re-sintering. The mechanism of thermal conductivity and electrical conductivity was analyzed. The n-particles’ influence was emphasized on the thermal and electrical conductivity. The relation between the thermal and electrical conductivity of the composite was compared with Lorents constant. The ratio of the thermal and electrical conductivity of the composite didn’t equal to Lorents constant. The composites were treated by solid solution and aging. The behaviour of n-particle, Zr and Cr was analyzed. The optional technology for heat treatment was obtained.The optional properties of the composites, the tensile strength ,the bending strength, the softening temperature of the composites are 600MPa, 401MPa, > 700℃respectively made using the process, 500MPa pressing, 900℃sintering , then 600MPa re-pressing, 900℃re-sintering. Using the above preparation conditions the composite was made into a kind of spot welding electrode. The performance of the electrode was rationalized on the spot. The axial shortage of the electrode and the number of welding dots were recorded. Comparing with the commercial spot welding electrode’s life, that of the self-made composite electrode was raised by 20%. The microstructure of the dis-functional composite electrode was characterized by OM, SEM, TEM. The dis-functional mechanism of the composite electrode was analyzed and the reason for long life was summoned.更多还原