Amorphous Steels: Atomic Structure Characterization via Experiment and Modeling

技术：材料科学和凝聚态物理学中的一个关键问题是了解在一些合金中出现而在另一些合金中不出现的大块玻璃形成的原因。现在是扩大金属合金基础研究的时候了，因为最近发现的大块非晶态金属为新的工业应用打开了可能性。该项目的目标有两个：1)结合实验结构表征和分子动力学(MD)模拟--对非晶态金属进行测量和建模，以确定原子和纳米尺度的结构；2)了解结构-性质关系--将建模结果与热力学性质相关联；研究非晶相中观察到的结构特征与脆性-延展性。例如，非晶态结构中的自由体积大小可以决定非晶态金属的延展性。目标是确定玻璃形成能力的驱动机制的基本特征，并了解在地方一级发生的热力学、动力学和结构过程之间的竞争机制。通过一个综合的研究和教育计划，该项目将通过让学生积极参与实施理论建模和实验工具来了解新型非晶态合金的玻璃形成能力来实现。这些合金的块状玻璃能力可能会导致新的技术应用，利用它们远远超过纯金属、传统金属玻璃和晶体的性能。用散射技术研究具有不同玻璃形成能力和晶化行为的铁基合金中具有代表性的非晶态金属，以获得它们的局部拓扑排列。这些将与从头算量子力学计算相结合，解决可能导致关于玻璃形成能力的重要揭示和对新的大块金属玻璃成分的预测的基本问题。非技术性：科学上，对新型非晶态金属的研究可以加速开发一种模拟复杂合金的新方法。此外，它还可能导致对玻璃形成能力和结构-性能关系的新预测，以指导和刺激新结构材料的设计。该项目的性质是跨学科和协作性的。它包括通过使用中子/X射线探头来研究原子结构的样品表征，这将使学生能够理解结构与性质的关系。该项目还涉及从头算建模和模拟，其中包括与另一所大学的合作。项目目标是通过构建从实验输出直接验证模型的基础来弥合大规模建模和实验之间的差距。这两种方法的结合将为本科生和研究生提供宝贵的培训和研究经验。该项目将成为至少一名研究生的博士论文。长期计划包括扩大与其他大学研究类似系统的其他小组的合作，以开发一个项目，使非晶态材料的本地结构建模能力得到广泛应用。

TECHNICAL: A key issue in materials science and condensed matter physics is to understand the reasons for bulk glass formation that occurs in some alloys and not in others. The time is now right to expand on the fundamental study of metallic alloys as recent discoveries of bulk amorphous metals have opened up the possibilities for new industrial applications. The objective of this project is twofold: 1) Combine experimental structural characterization and molecular dynamics (MD) simulation- Measurement and modeling of amorphous metals to determine the atomic and nanoscale structures; and 2) Understand structure-property relationships - Relate results from modeling to thermodynamic properties; investigate brittle-ductile properties to structural features observed in the amorphous phase. For example, the amount of free volume in the amorphous structure may determine the ductility of the amorphous metal. The goal is to define the essential features of the driving mechanism of the glass forming ability and to understand the competing mechanisms among the thermodynamic, kinetic and structural processes that take place at a local level. Through an integrated research and educational program, the project will be realized by involving the active participation of students in implementing theoretical modeling and experimental tools to understanding glass forming ability in new amorphous alloys. The bulk glass capabilities of these alloys will potentially lead to new technological applications that make use of their properties that far exceed those of pure metals, conventional metallic glasses and crystals. Representative amorphous metals of Fe-based alloys that exhibit different glass forming abilities and crystallization behaviors will be investigated by scattering techniques to obtain their local topological arrangement. These will be combined with ab-initio quantum mechanical calculations addressing fundamental issues that can lead to important revelations about glass formation ability and predictions of new bulk metallic glass compositions. NON-TECHNICAL: Scientifically, the study of novel amorphous metals could accelerate the development of a new approach to modeling complex alloys. Additionally, it could also lead to new predictions of glass forming ability and structure-property relationships for guiding as well as stimulating the design of new structural materials. The nature of the program is interdisciplinary and collaborative. It involves sample characterization through the use of neutron/x-ray probes for the investigation of atomic structures that will allow students to understand structure-property relationships. The project also involves ab-initio modeling and simulation that includes collaboration with another university. Project goal is to bridge the gap between large-scale modeling and experiment by constructing a foundation for direct validation of models from the experimental output. The combination of both approaches will provide valuable training and research experience for undergraduates and graduate students. This project will become the PhD thesis of at least one graduate student. The long term plans include expanding the collaboration with other groups from other universities that work on similar systems to develop a program where the local structure-modeling capabilities of amorphous materials become widely available.