Determining Phase Stability in the Co-Al-W System using First Principles Methods
- Degree Grantor:
- University of California, Santa Barbara. Materials
- Degree Supervisor:
- Matthew R. Begley
- Place of Publication:
- [Santa Barbara, Calif.]
- Publisher:
- University of California, Santa Barbara
- Creation Date:
- 2015
- Issued Date:
- 2015
- Topics:
- Materials science
- Keywords:
- Phonons,
Phase stability,
Cluster expansion,
Superalloy,
Cobalt, and
Density functional theory - Genres:
- Online resources and Dissertations, Academic
- Dissertation:
- M.S.--University of California, Santa Barbara, 2015
- Description:
Co-based superalloys are a promising new material for high strength, high temperature applications due to their gamma-gamma' microstructure. Within the Co-Al-W ternary system, the gamma' phase manifests as an L1 2 structure in a small temperature range. Determining the thermodynamic stability of the L12 phase relative to other phases in this system is important for guiding the alloy development process. Density functional theory allows the direct calculation of free energy for these phases. The configurational energy component of the energy for the L12 structure was calculated via a cluster expansion, and the vibrational energy component for all structures was calculated in the quasiharmonic approximation. The results show that the L12 structures become stable at 600K and increase stability at higher temperatures, which has not been shown in previous work.
The purpose of this thesis is both to show the encouraging research results in the Co-Al-W system, and also to be a useful guide for performing first principles calculations and connecting theory, VASP usage, and the utilization of the CASM code.
- Physical Description:
- 1 online resource (42 pages)
- Format:
- Text
- Collection(s):
- UCSB electronic theses and dissertations
- Other Versions:
- http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:1603369
- ARK:
- ark:/48907/f30z71gs
- ISBN:
- 9781339218090
- Catalog System Number:
- 990045865290203776
- Copyright:
- Philip Dodge, 2015
- Rights:
- In Copyright
- Copyright Holder:
- Philip Dodge
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Access: Public access | |
Dodge_ucsb_0035N_12655.pdf | pdf (Portable Document Format) |