Metastable β titanium alloys stand out as prominent candidates for structure materials in aerospace industries due to their light weight and exceptional high strength. This dissertation systematically investigates the microstructural evolutions in the metastable β Ti-5Al-5Mo-5V-3Cr (wt. %, Ti5553) alloy induced by various defects including grain boundary, twin boundary, and dual-phase interface using advanced characterization techniques such as transmission Kikuchi diffraction (TKD), 3D FIB-SEM tomography, and 4D STEM. Firstly, the morphology of grain boundary α precipitates was characterized using quantitative 3D FIB-SEM tomography combined with 3D phase field simulation. Our findings highlighted the critical role of the inclination angle between habit plane of α and grain boundary plane in determining the morphology of grain boundary α precipitates. Secondly, the nanoscale substructures of a novel high-indexed {10 9 3} twin and its influence on the formation of hierarchical α microstructure were studied, employing conventional TEM and aberration-corrected STEM. Thirdly, the early stage α nucleation in Ti-5553 was studied utilizing interrupted heat treatments and ex-situ characterizations via TEM and aberrationcorrected STEM. Our findings indicated that the preformed β/ω interface can act as nucleation sites for α precipitates. Lastly, the microstructure and defects in the direct energy deposited (DEDed) Ti-5553 alloy were investigated. The results demonstrate that the addition of stainless steel 316L can significantly refine the grain size while also introducing different defects.
| Identifer | oai:union.ndltd.org:unt.edu/info:ark/67531/metadc2332597 |
| Date | 05 1900 |
| Creators | Li, Dian |
| Contributors | Zheng, Yufeng, Banerjee, Rajarshi, Vasudevan, Vijay K., Mukherjee, Sundeep, Siller Carrillo, Héctor Rafael, Liao, Yiliang |
| Publisher | University of North Texas |
| Source Sets | University of North Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | Text |
| Rights | Public, Li, Dian, Copyright, Copyright is held by the author, unless otherwise noted. All rights Reserved. |
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