EAGER: Stability and Nanocrystallization Kinetics of Amorphous Al Alloys

块状纳米结构合金的一种重要形式是基于纳米晶体在无定形基质中的高密度分散。从无定形基质结晶是优选的合成方法，以允许控制和定制微结构，并因此控制和定制诸如高强度的性能。由于强度取决于颗粒的尺寸和体积分数，了解和控制原铝颗粒的形成机制，数密度为1021？1023 m-3分散在无定形基质中的纳米颗粒是特别感兴趣的。虽然这种微结构设计的技术意义是明确的，控制成核和生长动力学的基本理解还没有解决的早期阶段的纳米晶体的演变。此外，最近的纳米结构分析表明，在非晶相的原子排列是空间异质性，使一个新的模型，将在这项研究中提出的是需要考虑的空间异质性的动力学效应。为了提供数据库来检验未经证实的动力学分析的准确性，本文将系统地研究Al-Y-Fe非晶合金中微量合金化过程中的晶界形核和结构表征。从一个成功的项目的一个重要成果将是制定一个新的范例的动力学分析的纳米级微观结构合成的异质materials.NON-TECHNICAL摘要：纳米级的微观结构演变过程中的非晶合金在散装体积的主要结晶是负责有吸引力的结构和功能材料的性能，在运输和通信的技术应用。为了开发纳米级微结构，必须了解控制反应动力学，以便使纳米数密度最大化并限制生长。以前的动力学模型处理的非晶相均匀的原子尺度上，但最近的结构分析揭示了原子尺度的空间异质性。本文提出了一种新的动力学分析方法来处理非晶态Al-Y-Fe合金的空间非均匀状态，并用X射线形核测量进行了检验。这些结果与许多金属玻璃中常见的析晶反应--初晶的性质有更广泛的相关性。该项目工作的一个重要组成部分将是研究生的教育和本科生和高中生的研究经验。此外，纳米结构材料的讲座演示将被纳入高中和即将入学的本科生的校园外展计划。

TECHNICAL SUMMARY: An important form of bulk nanostructured alloys is based upon a high density dispersion of nanocrystals in an amorphous matrix. Crystallization from an amorphous matrix is a preferred synthesis method in order to allow the control and tailoring of the microstructure and therefore properties such as high strength. Since the strength depends on the particle size and volume fraction, understanding and controlling the mechanisms of primary aluminum nanocrystal formation with number densities of 1021 ? 1023 m-3 dispersed in an amorphous matrix are of special interest. While the technological significance of this microstructure design is clear, the fundamental understanding of the controlling nucleation and growth kinetics has not been resolved for the early stage evolution of nanocrystals. Moreover, recent nanoscale structural analysis has revealed that the atomic arrangements in the amorphous phase are spatially heterogeneous so that a new model that will be advanced in this study is required to account for the kinetic effects of spatial heterogeneities. In order to provide the database to test the fidelity of the unproven kinetics analysis, nanocrystal nucleation and structural characterization will be studied systematically in Al-Y-Fe amorphous alloys with minor alloying. An important outcome from a successful project will be the formulation of a new paradigm for the kinetics analysis of nanoscale microstructure synthesis in heterogeneous materials.NON-TECHNICAL SUMMARY: The nanoscale microstructures that evolve during primary crystallization of amorphous alloys in bulk volumes are responsible for the attractive structural and functional materials properties that have technological applications in transportation and communications. In order to develop nanoscale microstructures it is essential to understand the controlling reaction kinetics so that the nanocrystal number density is maximized and the growth is limited. Previous kinetics models have treated the amorphous phase as uniform on an atomic scale, but recent structural analysis has revealed atomic scale spatial heterogeneities. A new kinetics analysis will be developed to treat the spatially heterogeneous state and tested with nanocrystal nucleation measurements in amorphous Al-Y-Fe alloys. The results have a broader relevance to the nature of primary crystallization as a common devitrification reaction in many metallic glasses. An important component of the project effort will be the education of graduate students and the research experience for undergraduate and high school students. Further, lecture demonstrations on nanostructured materials will be incorporated into campus outreach programs for high school and incoming undergraduate students.