【作者】 侯贤华；

【导师】 高英俊；

【作者基本信息】 广西大学 ， 凝聚态物理， 2006， 硕士

【摘要】 Al-Cu-Mg合金具有高比强度和比模量，良好的耐蚀性和优异的高温特性，是一种新型硬质航空航天结构材料。但目前对Al-Cu-Mg合金的结构与性能的微观机理研究仍处于探索阶段。本文运用固体与分子经验电子理论(简称EET理论)，并结合程开甲院士改进的TFD方法，系统地研究了Al-Cu-Mg三元合金在时效过程中各种偏聚晶胞及部分析出相的价电子结构和界面电子结构及其与性能的关系，为该合金的进一步开发研究提供理论依据。主要研究内容如下： 1．建立Al-Cu-Mg合金中存在各相的价电子结构模型，认为固溶体中包含了五类晶胞：α-Al晶胞、Al-Mg晶胞、Al-Cu晶胞、Al-Cu-Mg晶胞和含有空位的各种晶胞。运用平均原子模型计算了这些晶胞的价电子结构。结果表明三元偏聚晶胞的共价电子对数数目较多，具有一定的固溶强化作用；特别是含有空位的偏聚晶胞中溶质原子的杂化能级偏低，则具有较低的自由能，所以一般含有空位的偏聚晶胞是最优先形核的胚芽。 2．对Al-Cu-Mg合金的过饱和固溶体在时效过程中析出的G．P．B区、S″和S相价电子结构进行了计算，从电子结构合理解释了GPB区向S″相转变的相变过程。并就这些析出相对合金性能的影响进行了讨论。 3．对Al-Cu-Mg合金的基体α-Al与偏聚晶胞和析出相界面，如α-Al／Al-Mg界面、α-Al／Al-Cu界面、α-Al／Al-Cu-Mg界面、α-Al／Al-Mg-Vac界面、α-Al／GPBZ、α-Al／S″界面的界面电子结构进行计算，结果表明α-Al／S″界面非常连续，并从界面电子结构层次讨论了合金界面强化与相变过程。 4．对Al-Cu-Mg合金中重要的析出相GPB区，亚稳定S″相及稳定S相的总成键能力做了计算，结果表明S相的总键能最大，并从键能的角度分析了该析出相对合金性能的影响。更多还原

【Abstract】 Al-Cu-Mg alloys have excellent performances, such as high specific strength, high specific modulus, good corrosion resistance and high temperature properties. They are widely used in aerospace as a new kind of structural material. However, the study for the microscopic mechanism of structure and properties in Al-Cu-Mg alloys is still in exploration stage now.The valence electron structures and interface electron structures in all kinds of segregating cells and part of precipitate phases during aging in Al-Cu-Mg alloys were analyzed systematically using the Empirical Electronic Theory in solid and molecules (EET) and improved TFD method by Cheng Kaijia. The research work made it possible to further study as theoretical method. The main contents of this paper are as follows:Firstly, the models for valence electron structures of phases in Al-Cu-Mg alloys were established. There are five kinds of cells in Al-Cu-Mg alloys: α-Al cell; Al-Cu cell; Al-Mg cell; Al-Cu-Mg cell and all kinds of cells containing vacancies. The valence electron structures of above cells were calculated based on the average atom model. The results suggest that there are more valence electrons in ternary segregating cells, which can strengthen the matrix. Especially, the energy level of solute atom is lower in the segregating cells containing vacancy, thus the free energy is lower too, and so the embryos or precursor structure will first form in the segregating cells containing vacancies.Secondly, the valence electron structures of G.P.B zone, S" phase and S phase in supersaturated solid solution during aging were calculated in Al-Cu-Mg alloys. The phase transformation from GP.B zone to S" phase was interpreted reasonably based on valence electron structures. And then,更多还原