CAREER: Neutron, Synchrotron X-ray Diffraction and Instrumented Indentation Studies of Deformation in Shape-Memory Alloys

形状记忆合金因其表现出的变形现象——孪生和应力诱导或温度诱导的相变——而具有理论和商业价值。该程序采用中子衍射、同步加速器x射线衍射和仪器压痕来研究形状记忆合金的变形。重点是原位衍射测量，即同时记录受到外部应力或温度变化或其组合的样品的衍射光谱。这些测量提供了在孪晶和应力诱导或温度诱导相变过程中不断变化的内部应变、织构和相体积分数的定量信息。这些实验将利用洛斯阿拉莫斯国家实验室的中子束和阿贡国家实验室的同步加速器x射线束。根据研究形状记忆合金变形的主题和从小体积形状记忆合金中获得力学性能的目标，将对形状记忆合金进行仪器压痕实验，以将压痕实验的载荷深度数据与常规测试的宏观应力应变数据相关联。该计划预计将进一步理解(a)形状记忆合金用于执行器应用和生物医学应用，因为形状记忆合金继续作为支架材料的选择，以及(b)中子衍射、同步x射线衍射和仪器微纳米压痕作为新兴材料、体、涂层、薄膜、线和点形式的内应力力学表征的有价值的工具。教育活动包括课程开发、教学和实验室开发，为学生使用国家实验室的设施提供经验和培训。拓展和指导活动包括与当地科学中心和UCF的少数民族工程和计算机科学办公室合作，通过佛罗里达工程教育交付系统（FEEDS）的远程教育在工作场所进行工程教育，以及开发行业短期课程。

Shape-memory alloys are of theoretical and commercial interest for the deformation phenomena they exhibit - twinning and stress-induced or temperature-induced phase transformations. The proposed program uses neutron diffraction, synchrotron X-ray diffraction and instrumented indentation to investigate deformation in shape-memory alloys. The emphasis is on in situ diffraction measurements, i.e., simultaneously recording diffraction spectra from samples that are subjected to external stresses or temperature changes, or a combination thereof. Such measurements provide quantitative information of the evolving internal strains, texture and phase volume fractions during twinning and stress-induced or temperature-induced phase transformations. The experiments will utilize the neutron beam at Los Alamos National Laboratory and the synchrotron X-ray beam at Argonne National Laboratory. Consistent with the theme of investigating deformation in shape-memory alloys and with the objective of obtaining mechanical properties from small sampling volumes of shape-memory alloys, instrumented indentation experiments will be performed on shape-memory alloys to correlate load-depth data from indentation experiments with macroscopic stress-strain data from conventional tests.The program is expected to further the understanding of (a) shape-memory alloys for actuator applications and for biomedical applications, as shape-memory alloys continue to make inroads as the material of choice for stents, and (b) neutron diffraction, synchrotron X-ray diffraction and instrumented micro- and nanoindentation as valuable tools for mechanical characterization of internal stresses in emerging materials, bulk, coatings, thin-films, line and dot forms. The educational activities include curriculum development, instruction and laboratory development providing experience and training for students using facilities at National Laboratories. Outreach and mentoring activities include collaboration with a local science center and the Minority Engineering and Computer Science Office at UCF, engineering education in the work place through distance education in the Florida Engineering Education Delivery System (FEEDS) and the development of industry short-courses.