Study of the Influence of Hydrogen on the Microstructure and Properties of Intermetallic Alloys

9501017 De Graef这项研究计划旨在深入了解氢对金属间化合物合金中选定相的稳定性和性质的影响，识别和评估这些系统中稳定和亚稳定的氢化物，并开发适用于高温富氢环境中应用的微观结构。这是通过对选定的合金进行气相充电、表征微观结构变化和测量机械性能变化来实现的。该程序试图通过使用能量过滤的电子显微镜来研究氢向位错核心区的偏析，来评估氢致脆化的氢增强局域塑性(HELP)模型。这一研究计划的结果将引起工程界的兴趣，因为新的微结构将被创造出来，提高对氢环境有害影响的抵抗力。该计划的教育部分包括三个部分：(1)创建一个本科生视觉实验室，并对现有的实验课程进行调整，以充分利用该实验室提供的新的实验机会；(2)开发用于二年级本科生核心课程的多媒体课件；以及(3)为研究生水平的电子光学课程创建一个互动课件设施。本科生视觉实验室将成为这一教育发展计划的整合因素，并将为外展活动提供新的机会。金属间化合物合金在氢气气氛中的%结构性能退化是这些合金在氢基推进系统中应用的主要问题。最初的重点是钛铝化物金属间化合物，它们在飞机发动机和高超声速飞行器中有潜在的应用。***

9501017 De Graef This research program is aimed at an in-depth understanding of the effect of hydrogen on the stability and properties of selected phases in intermetallic alloys, identifies and evaluates stable and metastable hydrides in these systems, and develops appropriate microstructures for applications in high temperature hydrogen-rich environments. This is accomplished by gas-phase charging of selected alloys, characterization of the microstructural changes, and measurement of changes in the mechanical properties. The program attempts to evaluate the hydrogen enhanced localized plasticity (HELP) model for hydrogen-induced embrittlement by using energy filtered transmission electron microscopy to study hydrogen segregation to the core region of dislocations. Results of this research program will be of interest to the engineering community since novel microstructures will be created with improved resistance against the detrimental effects of hydrogen environments. The educational part of the program consists of three parts: (1) creation of an Undergraduate Vision Laboratory and adaptation of the current laboratory courses to fully benefit from the novel experimeltal opportunities offered by the lab; (2) development of Multi-Media Courseware for use in the sophomore level undergraduate core-classes; and (3) creation of an interactive courseware facility for the graduate level electron optics class. The Undergraduate Vision Lab will be the integrating factor in this educational development plan and will provide new opportunities for outreach activities. %%% Degradation of structural properties of the intermetallic alloys in a hydrogen atmosphere is a major concern for the application of these alloys in hydrogen-based propulsion systems. The initial focus is on titanium aluminide intermetallics, which have potential applications in aircraft engines and hypersonic vehicles. ***