Materials World Network: Structures and Mechanical Behavior of Nanocrystalline Phase-Containing Glass-Forming Thin Films

该材料世界网络奖由田纳西大学诺克斯维尔分校材料研究部的金属材料和纳米结构项目颁发，旨在建立对非晶/纳米晶金属薄膜涂层的加工和制造以及导致延展性和抗疲劳性增强的机制的基本了解。 该奖项由特别项目办公室-DMR 和国际科学与工程办公室共同资助。这个合作实验和理论项目是田纳西大学和中华民国（台湾）的团队进行的，该团队由国立台湾科技大学、国立台湾海洋大学和国立成功大学组成。该项目的动机是两个团队最近发现的两个新颖的初步观察结果：1）可以通过退火诱导的非晶化工艺制备含有或不含有纳米晶相的金属玻璃涂层； 2）结构材料上的这些涂层表现出优异的机械性能和抗疲劳性。在实验计划中，台湾团队将开发和改进薄膜制备方法，实现退火过程中的可控非晶化和纳米晶化，而美国团队将重点研究这些基片薄膜系统的变形和疲劳行为。先进的表征工具，如高分辨率透射电子显微镜，将用于研究（1）薄膜制备过程中的微观结构演变，以及（2）机械测试过程中应变局部化和金属玻璃薄膜中纳米晶相的相互作用。从建模角度来看，台湾团队将侧重于退火诱导非晶化动力学过程的分子动力学研究，而美国团队将致力于剪切带特性与薄膜力学行为的关系，以及薄膜对疲劳行为的影响。这些模型与实验观察的联系和比较将导致对疲劳机制的基本理解。合作研究将推进和加强美国和台湾双方的重点研究和教学活动。该联合项目的研究项目将被设计并用作初高中学生和教师的教学单元，特别是参与外展项目的女性和少数民族学生。这些努力不仅是为了提高公众对先进结构材料及其科学重要性的认识，也是为了激发更广泛公众对科学、工程和技术职业的兴趣。教育材料将通过两个新开发的研究生课程来开发和传播。目前的综合研究和教育活动将提高公众对国际科学合作的认识。

This Materials World Network award by the Metallic Materials and Nanostructures program in the Division of Materials Research to University of Tennessee Knoxville is to establish a fundamental understanding of the processing and fabrication of amorphous/nanocrystalline metallic thin-film coatings, and the mechanisms responsible for the resulting ductility and fatigue-resistance enhancements. This award is cofunded by the Office of Special Projects-DMR and the Office of International Science and Engineering. This collaborative experimental and theoretical project is carried out between the University of Tennessee and the team in the Republic of China (Taiwan) consisting of National Taiwan University of Science and Technology, National Taiwan Ocean University and National Cheng Kung University. This project is motivated by two novel and preliminary observations that the two teams recently discovered that: 1) metallic-glass coatings with or without the presence of nanocrystalline phases can be prepared by an annealing-induced amorphization process; and 2) these coatings on structural materials demonstrate excellent mechanical properties and fatigue resistance. In the experimental program, the Taiwan team will develop and improve the thin-film preparation method that realizes the controllable amorphization and nanocrystallization during annealing, and the USA team will focus on the deformation and fatigue behavior of these film-on-substrate systems. Advanced characterization tools, such as the high-resolution transmission-electron microscopy, will be employed to study (1) the microstructural evolution during the thin-film preparation and (2) the interaction of the strain localization and the nanocrystalline phase in the metallic-glass film during mechanical testing. From the modeling point of view, the Taiwan team will emphasize a molecular-dynamics study of the kinetic processes in the annealing-induced amorphization, while the USA team will work on the relationship between the shear-band characteristics and the mechanical behavior of the film, and the effect of the film on the fatigue behavior. The connection of these models to and comparisons with the experimental observations will lead to the basic understanding of fatigue mechanisms. The collaborative research will advance and enhance the focused research and teaching activities on both the USA and Taiwan sides. Research projects from this joint program will be designed and used as a teaching unit for both middle- and high-school students and teachers, especially women and minority students involved in the outreach programs. These efforts are designed, not only to increase the public awareness of advanced structural materials and their scientific importance, but also to stimulate the interests of the broader public in science, engineering, and technology careers. Educational materials will be developed and disseminated through two newly-developed graduate-level classes. The present integrated research and education activities will promote the public awareness of the international-scientific collaboration.