msepostdoc-list FW: SEMINAR REMINDER: S. Lawrence, PhD Prelim I, Fri., 4/12/13, 11:30 am, ARMS 1028

[Stacey, Lisa A]

Please see seminar notice below:

MATERIALS SCIENCE AND ENGINEERING
SEMINAR


Mechanisms of Hydrogen Degradation in Metals

By:
Samantha Lawrence

Ph.D. Prelim Exam – Part I

Advisor:
Prof. D. F. Bahr

ABSTRACT

Hydrogen is an important energy carrier; however, there are substantial barriers to effective hydrogen transport and storage. Degradation of metallic systems exposed to hydrogen (especially those used in pressure vessels, tanks, and pipelines of various energy industries) leading to unexpected catastrophic failures is particularly disturbing. Hydrogen is linked to a decrease in ductility, fracture strength, and fracture toughness in many metals (the phenomenon of hydrogen embrittlement). Three broadly grouped degradation mechanisms have been identified: (1) hydride formation, where brittle hydride precipitates ease fracture by providing low energy crack paths; (2) hydrogen-enhanced localized plasticity (HELP), where localized deformation increases in the presence of hydrogen due to a decrease in barriers to dislocation motion; and (3) hydrogen-enhanced decohesion (HEDE), where hydrogen reduces interfacial atomic bond strengths resulting in a sharp transition between ductile and brittle fracture. Hydrogen diffusion and subsequent capture at microstructural inhomogeneities, or traps, is required to establish a critical H-concentration prior to failure. Realizing that a “one‑size‑fits‑all” mechanism explaining observations of hydrogen embrittlement is unlikely, proposed degradation mechanisms are presented and future work geared toward understanding the interrelationships between the mechanisms is proposed.



Date:         Friday, April 12, 2013

Time:      11:30 A.M.
Place:        ARMS 1028




Lisa Stacey
Secretary/Development Assistant
Purdue University
School of Materials Engineering
765/494-4100

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