Alexandria Digital Research Library

Determining Phase Stability in the Co-Al-W System using First Principles Methods

Author:
Dodge, Philip C.
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:
Density functional theory
Cobalt
Phonons
Cluster expansion
Superalloy
Phase stability
Genres:
Dissertations, Academic and Online resources
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
ARK:
ark:/48907/f30z71gs
ISBN:
9781339218090
Catalog System Number:
990045865290203776
Rights:
Inc.icon only.dark In Copyright
Copyright Holder:
Philip Dodge
File Description
Access: Public access
Dodge_ucsb_0035N_12655.pdf pdf (Portable Document Format)