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

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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. ***