Plastic flow and microstructure evolution in niobium at elevated temperatures
dc.contributor.advisor | Taleff, Eric M. | |
dc.contributor.committeeMember | Kovar, Desiderio | |
dc.contributor.committeeMember | Mangolini, Filippo | |
dc.contributor.committeeMember | Seepersad, Carolyn | |
dc.creator | Brady, Emily Ann Dukes | |
dc.date.accessioned | 2022-05-13T19:17:59Z | |
dc.date.available | 2022-05-13T19:17:59Z | |
dc.date.created | 2021-12 | |
dc.date.issued | 2021-12-09 | |
dc.date.submitted | December 2021 | |
dc.date.updated | 2022-05-13T19:18:00Z | |
dc.description.abstract | Plastic flow and microstructure evolution are investigated at elevated temperatures in two unalloyed niobium sheet materials, Type 1 and Type 2 as designated in ASTM B393-18. Tensile tests are conducted at temperatures from 1473 to 1823 K (1200 to 1550°C) at constant true strain rates of 10⁻³ and 10⁻⁴ s⁻¹. Deformation microstructures are characterized using backscatter electron (BSE) imaging, electron backscatter diffraction (EBSD), and high-resolution EBSD (HR-EBSD). The mechanical behaviors of the Type 1 and Type 2 niobium materials are compared to relevant data from the literature. Elevated temperature deformation in both niobium materials is dominated by the five-power creep mechanism and the associated development of subgrains. The higher impurity content of the Type 2 niobium led to: 1. greater strength, 2. delayed recrystallization, 3. slower grain growth, 4. inhomogeneous microstructures, and 5. slower recovery which resulted in finer and less distinct subgrains compared to the Type 1 niobium. The smaller subgrain size of the Type 2 niobium produces, through the five-power creep mechanism, a higher strength at elevated temperature compared to the Type 1 niobium. This is the first mechanistic explanation supported by direct microstructural data for how impurity content affects strength in refractory metals. HR-EBSD analysis is performed on the deformed Type 2 niobium material by developing new techniques to: 1. utilize data from a new EBSD instrument, 2. expand the capabilities of the OpenXY open-source cross-correlation software, and 3. enable cross correlation calculations spanning the breadth of heavily deformed grains. This is the first successful implementation of these techniques. | |
dc.description.department | Materials Science and Engineering | |
dc.format.mimetype | application/pdf | |
dc.identifier.uri | https://hdl.handle.net/2152/114155 | |
dc.identifier.uri | http://dx.doi.org/10.26153/tsw/41058 | |
dc.language.iso | en | |
dc.subject | Niobium | |
dc.subject | High-temperature deformation | |
dc.subject | Grain growth | |
dc.subject | Creep | |
dc.subject | Subgrains | |
dc.subject | Electron backscatter diffraction (EBSD) | |
dc.subject | Elastic modulus | |
dc.subject | High resolution electron backscatter diffraction | |
dc.title | Plastic flow and microstructure evolution in niobium at elevated temperatures | |
dc.type | Thesis | |
dc.type.material | text | |
thesis.degree.department | Materials Science and Engineering | |
thesis.degree.discipline | Materials Science and Engineering | |
thesis.degree.grantor | The University of Texas at Austin | |
thesis.degree.level | Doctoral | |
thesis.degree.name | Doctor of Philosophy |
Access full-text files
Original bundle
1 - 1 of 1
Loading...
- Name:
- BRADY-DISSERTATION-2021.pdf
- Size:
- 2.97 MB
- Format:
- Adobe Portable Document Format