CALPHAD Assessmentshttps://hdl.handle.net/11256/82026-04-07T10:20:46Z2026-04-07T10:20:46ZDevelopment of a Diffusion Mobility Database for Co-based SuperalloysCampbell, CarelynLindwall, GretaMoon, Kil-wonWilliams, MaureenTso, Whitneyhttps://hdl.handle.net/11256/9982023-03-22T00:25:12ZDevelopment of a Diffusion Mobility Database for Co-based Superalloys
Campbell, Carelyn; Lindwall, Greta; Moon, Kil-won; Williams, Maureen; Tso, Whitney
To facilitate the development of high-temperature Co-based gamma-gamma prime superalloys, a Co-Ni based diffusion mobility database is developed for the eight component FCC (Face Centered Cubic) system of Co-Al-W-Ni-Cr-Ti-Ta-Re. A CALPHAD approach is used to represent the temperature and composition dependency of the multicomponent system. The mobility descriptions are based on previous assessment work for the Ni-based superalloys, published experimental and computational data, and established diffusion correlations. The initial mobility descriptions were then refined using additional diffusion couple experimental data, particularly for the Co-Cr, Co-Ta, and Ni-Ta systems. After re-optimizing the descriptions with the new experimental data, the mobility descriptions were validated using a collection of published diffusion couple composition profiles, which were not included in the initial assessment process.
Thermodynamic analysis of the topologically close packed σ phase in the Co-Cr systemWang, PeishengPeters, Matthew C.Kattner, Ursula R.Choudhary, KamalOlson, Gregory Bhttps://hdl.handle.net/11256/9852019-02-19T00:12:13Z2019-11-01T00:00:00ZThermodynamic analysis of the topologically close packed σ phase in the Co-Cr system
Wang, Peisheng; Peters, Matthew C.; Kattner, Ursula R.; Choudhary, Kamal; Olson, Gregory B
Density functional theory (DFT) calculations show that it is essential to consider the magnetic contribution to the
total energy for the end-members of the σ phase. A more straightforward method to use the DFT results in a
CALPHAD (Calculation of phase diagrams) description has been applied in the present work. It was found that
only the results from DFT calculations considering spin-polarization are necessary to obtain a reliable description
of the σ phase. The benefits of this method are: the DFT calculation work can be reduced and the CALPHAD
description of the magnetic contribution is more reliable. A revised thermodynamic description of the CoeCr
system is presented which gives improved agreement with experimental phase boundary data for the σ phase.
2019-11-01T00:00:00ZThermodynamic assessment of the Co-Ta systemWang, PeishengKoßmann, JörgKattner, Ursula RPalumbo, MauroHammerschmidt, ThomasOlson, Gregory Bhttps://hdl.handle.net/11256/9842019-02-19T00:11:41Z2018-12-01T00:00:00ZThermodynamic assessment of the Co-Ta system
Wang, Peisheng; Koßmann, Jörg; Kattner, Ursula R; Palumbo, Mauro; Hammerschmidt, Thomas; Olson, Gregory B
The Co-Ta system has been reviewed and the thermodynamic description was re-assessed in the present work.
DFT (density functional theory) calculations considering spin polarization were performed to obtain the energies
for all end-member configurations of the C14, C15, C36 and μ phases for the evaluation of the Gibbs energies of
these phases. The phase diagram calculated with the present description agrees well with the experimental and
theoretical data. Considering the DFT results was essential for giving a better description of the μ phase at lower
temperatures.
2018-12-01T00:00:00ZThermodynamic Assessments of Bi-Te Bi-Se Sb-TePeters, Matthewhttps://hdl.handle.net/11256/9742018-08-02T19:36:44ZThermodynamic Assessments of Bi-Te Bi-Se Sb-Te
Peters, Matthew
The Bi-Te, Bi-Se, and Sb-Te systems have been assessed. The compounds Bi2Te3, Bi2Se3, and Sb2Te3 have been assessed using a 3 sublattice model and the intrinsic carriers of each compound have been assessed. The homologous series between the end-members have been assessed using a stoichiometric mixture of the end-members and a metastability has been assumed between them.