纳晶金属材料的制备与热输运行为研究

发布时间：2018-07-05 19:05

本文选题：纳晶材料 + 热导率　；参考：《华北电力大学》2017年硕士论文

【摘要】：伴随着科学技术的飞速发展,越来越多的新材料不断地被开发出来。纳晶材料与相应的传统材料相比具有较高的屈服强度和较好的耐磨性能,晶粒细化理论及技术已成为提高新型金属材料性能的重要研究方向。高强度和高韧性通常意味着晶粒的细化、晶体缺陷,同时第二相的加入,致使材料晶粒边界密度及边界的晶格体点阵畸变加剧,进而也加强了对运动电子的散射作用,导致材料导热性能显著恶化。因此,进一步探究并掌握新兴材料的导热性能成为工作的重点。为了更好地了解纳晶金属材料导热特性和热输运机理,本文主要工作是选用高纯Cu、Ag粉体,利用国产六面顶压机DS6×14 MN制备得到纳晶Cu和纳晶CuAg双峰材料,对样品材料物性参数等进行了测试。同时,分析并简化纳晶金属材料热输运几何单元模型,引入卡皮查热阻理论,在该理论基础上建立并改进卡皮查热阻数学模型,对两种试样热导率进行了数值计算预测,从新的视角讨论纳晶金属材料内部晶界等因素所引起的载热子散射效应对热输运过程的影响及其内在的物理机理和构效关系,对揭示纳米结构金属晶体热输运机理和实际中材料热设计水平提升都有重要意义。本文的研究结果表明,相对于粗晶体而言,热压烧结得到的纳晶Cu和纳晶CuAg双峰材料导热性能明显削弱。平均晶粒尺寸约在50-200 nm范围内纳晶Cu热导率与晶粒尺寸约在50-300nm的纳晶Cu-Ag合金材料热导率平均值大约为其相对应粗晶材料热导率的55%和40%。另外,其热导率随晶粒尺寸的增加而增,表现出显著的尺寸效应。通过数值模型预测了平均晶粒尺寸在纳米级的纳晶Cu和纳晶CuAg材料的热导率,计算得到的热导率随晶粒尺寸的减小而减小;当晶粒尺寸小于0.5μm时,热导率随晶粒尺寸的变化剧烈,尺度依赖效应加剧,与实验结论一致。
[Abstract]:With the rapid development of science and technology, more and more new materials have been developed. Nanocrystalline materials have higher yield strength and better wear resistance than traditional materials. Grain refinement theory and technology have become an important research direction to improve the properties of new metal materials. High strength and high toughness usually mean grain refinement, crystal defects, and the addition of the second phase, which results in the aggravation of grain boundary density and lattice distortion of the boundary, which also enhances the scattering of moving electrons. The thermal conductivity of the material deteriorated significantly. Therefore, to further explore and grasp the thermal conductivity of emerging materials has become the focus of work. In order to better understand the thermal conductivity and thermal transport mechanism of nanocrystalline metal materials, the main work of this paper is to prepare nanocrystalline Cu and nanocrystalline CuAg bimodal materials using home-made six-sided top press DS6 脳 14 MN. The physical properties of the samples were tested. At the same time, the geometric model of thermal transport of nanocrystalline metal materials is analyzed and simplified, and the Kapicha thermal resistance theory is introduced. On the basis of this theory, the mathematical model of thermal resistance of two kinds of samples is established and improved, and the thermal conductivity of two samples is numerically calculated and predicted. From a new angle of view, the influence of the heat carrier scattering effect on the thermal transport process, the physical mechanism and the structure-activity relationship of nanocrystalline metal materials caused by factors such as grain boundary are discussed. It is of great significance to reveal the thermal transport mechanism of nanocrystalline metal crystals and improve the thermal design level of materials in practice. The results show that the thermal conductivity of nanocrystalline Cu and nanocrystalline CuAg bimodal materials is obviously weakened compared with coarse crystals. The average thermal conductivity of nanocrystalline Cu and nanocrystalline Cu-Ag alloy in the range of 50-200 nm is about 55% and 40% of the corresponding coarse-grained material. In addition, the thermal conductivity increases with the increase of grain size, showing a significant size effect. The thermal conductivity of nanocrystalline Cu and nanocrystalline CuAg materials with average grain size is predicted by numerical model. The calculated thermal conductivity decreases with the decrease of grain size, and when the grain size is less than 0.5 渭 m, the thermal conductivity of nanocrystalline Cu and nanocrystalline CuAg is predicted. The thermal conductivity varies sharply with the grain size, and the scale dependent effect is aggravated, which is consistent with the experimental results.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG14

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