Multiscale Microstructural Investigation of the Ductile Phase Toughening Effect in a Bi-phase Tungsten Heavy Alloy

A specialty class of alloys known as tungsten heavy alloys (WHAs) possess extremely desirable qualities for adoption in nuclear fusion reactors. Their high temperature stability, improvement in fracture toughness over other brittle candidates, and promising performance in initial experimental trials have demonstrated their utility, and recent advancements have been made in understanding and applying these multiphase materials systems. To that end, Pacific Northwest National Laboratory in collaboration with Virginia Tech have sought to understand and tailor the structure and properties of these materials to optimize them for service in fusion reactor interiors; thereby improving the robustness, efficiency, and longevity of structural materials selected for service in an extremely hostile environment. In this analysis of material viability, a multiscale investigation of the connections between structure-property relationships in these multiphase composite microstructures has been undertaken, employing advanced characterization techniques to bridge the macro, micro, and nanoscales for the purpose of generating a framework for the understanding of the ductile phase toughening effect in these systems. This analysis has yielded evidence suggesting the effectiveness of WHA microstructures in the simultaneous expression of high strength and toughness owes to the intimately bonded nature of the boundary which exists between the dissimilar phases in these bi-phase microstructures. Analytical techniques have been employed to provide added dimensionality to traditional materials characterization techniques, providing the first three-dimensional microstructure reconstructions exhibiting the effects of thermomechanical processing on these dual-phase microstructures, and the first time-resolved approach to the observation of WHA deformation through in-situ uniaxial tension testing. The contributions of purposefully introduced microstructural anisotropy and its contribution to texturing and boundary conformations is discussed, and an emphasis has been placed on the study of the interface between the dissimilar phases and its role in the overall expression of ductile phase toughening. In short, this collective work utilizes multiscale and multidimensional characterization techniques in the in-depth analysis and discussion of WHA systems to connect their structure to the properties which make them excellent candidates for fusion reactor systems.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Materials Science and Engineering

Department dc:contributor.department

Materials Science and Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2022

Author dc:creator

• Haag IV, James Vincent

Chair dc:contributor.committeechair

• Murayama, Mitsuhiro

Committee members dc:contributor.committeemember

• Robertson, Jennifer E.
• Bai, Xianming
• Edward, Danny J.
• Reynolds, William T. Jr.

• Tungsten Heavy Alloy
• SEM
• TEM
• Orientation Relationship
• 3D Microstructure Reconstruction
• In-Situ

Statement dc:rights

• Creative Commons Attribution 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Dc Identifier Other

vt_gsexam:34690

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/110440