本文選題：納晶材料 + 熱導率��； 參考：《華北電力大學》2017年碩士論文

【摘要】：伴隨著科學技術的飛速發(fā)展,越來越多的新材料不斷地被開發(fā)出來。納晶材料與相應的傳統(tǒng)材料相比具有較高的屈服強度和較好的耐磨性能,晶粒細化理論及技術已成為提高新型金屬材料性能的重要研究方向。高強度和高韌性通常意味著晶粒的細化、晶體缺陷,同時第二相的加入,致使材料晶粒邊界密度及邊界的晶格體點陣畸變加劇,進而也加強了對運動電子的散射作用,導致材料導熱性能顯著惡化。因此,進一步探究并掌握新興材料的導熱性能成為工作的重點。為了更好地了解納晶金屬材料導熱特性和熱輸運機理,本文主要工作是選用高純Cu、Ag粉體,利用國產六面頂壓機DS6×14 MN制備得到納晶Cu和納晶CuAg雙峰材料,對樣品材料物性參數(shù)等進行了測試。同時,分析并簡化納晶金屬材料熱輸運幾何單元模型,引入卡皮查熱阻理論,在該理論基礎上建立并改進卡皮查熱阻數(shù)學模型,對兩種試樣熱導率進行了數(shù)值計算預測,從新的視角討論納晶金屬材料內部晶界等因素所引起的載熱子散射效應對熱輸運過程的影響及其內在的物理機理和構效關系,對揭示納米結構金屬晶體熱輸運機理和實際中材料熱設計水平提升都有重要意義。本文的研究結果表明,相對于粗晶體而言,熱壓燒結得到的納晶Cu和納晶CuAg雙峰材料導熱性能明顯削弱。平均晶粒尺寸約在50-200 nm范圍內納晶Cu熱導率與晶粒尺寸約在50-300nm的納晶Cu-Ag合金材料熱導率平均值大約為其相對應粗晶材料熱導率的55%和40%。另外,其熱導率隨晶粒尺寸的增加而增,表現(xiàn)出顯著的尺寸效應。通過數(shù)值模型預測了平均晶粒尺寸在納米級的納晶Cu和納晶CuAg材料的熱導率,計算得到的熱導率隨晶粒尺寸的減小而減小;當晶粒尺寸小于0.5μm時,熱導率隨晶粒尺寸的變化劇烈,尺度依賴效應加劇,與實驗結論一致。
[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.
【學位授予單位】：華北電力大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG14

【參考文獻】

相關期刊論文 前5條

1 黃叢亮;馮妍卉;張欣欣;李靜;王戈;O窗，

本文編號：2101412