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

这项由美国田纳西大学诺克斯维尔分校材料研究部金属材料和纳米结构项目颁发的材料世界网络奖旨在建立对非晶/纳米晶体金属薄膜涂层的加工和制造的基本理解，以及由此产生的延展性和抗疲劳性增强的机制。该奖项由dmr特别项目办公室和国际科学与工程办公室共同资助。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)通过退火诱导非晶化工艺可以制备具有或不具有纳米晶相的金属玻璃涂层；2)涂层在结构材料上表现出优异的力学性能和抗疲劳性能。在实验项目中，台湾团队将开发和改进薄膜制备方法，实现退火过程中可控的非晶化和纳米化，美国团队将重点研究这些薄膜-衬底系统的变形和疲劳行为。高分辨率透射电镜等先进表征工具将用于研究(1)薄膜制备过程中的微观结构演变；(2)力学测试过程中金属玻璃薄膜中应变局部化与纳米晶相的相互作用。将这些模型与实验观察相结合并与之比较，将有助于对疲劳机理的基本认识。合作研究将促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作为初高中学生和教师的教学单元，特别是参与外展项目的妇女和少数民族学生。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，而且也是为了激发更广泛的公众对科学、工程和技术事业的兴趣。将通过两个新开设的研究生班编写和传播教育材料。目前的综合研究和教育活动将促进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.