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 Title: The effects of hydrogen on the deformation and fracture behavior of the metastable beta-titanium alloy, TIMETAL(RTM) 21S Author(s): Teter, David F. Doctoral Committee Chair(s): Robertson, Ian M. Department / Program: Engineering, MetallurgyEngineering, Materials Science Discipline: Engineering, MetallurgyEngineering, Materials Science Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Engineering, Metallurgy Engineering, Materials Science Abstract: The metastable $\beta$-titanium alloy, TIMETAL$\sp\circler$ 21S, exhibits a sharp ductile-to-brittle transition when the hydrogen concentration is increased slightly above H/M $=$ 0.22. To understand this sharp transition, a series of experiments was devised to test for the possible hydrogen embrittlement mechanisms. In situ straining experiments in an environmental cell TEM showed that hydrogen enhances the mobility of dislocations. However, this mechanism cannot account for the abrupt transition that is observed. No evidence for the formation of hydrides on fracture surfaces or in the stress fields of active cracks was found suggesting that the stress-induced hydride mechanism is not responsible for the observed transition. Therefore, the most viable mechanism is hydrogen-induced decohesion. Bulk testing showed that internal hydrogen reduces the yield strength of ductile specimens and decreases the fracture stress of the brittle specimens. All of the observed phenomena are consistent with a decohesion mechanism. Issue Date: 1996 Type: Text Language: English URI: http://hdl.handle.net/2142/22426 ISBN: 9780591199390 Rights Information: Copyright 1996 Teter, David F. Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9712457 OCLC Identifier: (UMI)AAI9712457
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