https://hdl.handle.net/11256/6 2026-04-25T00:08:30Z 2026-04-25T00:08:30Z Lass, Eric A. https://hdl.handle.net/11256/824 2023-05-02T13:22:03Z

Co-(Ni)-Al-W alloy DSC measured temperatures: Curie, solvus, solidus, and liquidus temperatures Lass, Eric A. Co-(Ni)-Al-W Ternary and Quaternary DSC measured Curie, solvus, solidus, and liquidus temperatures.

Shinagawa, Kazuya Chinen, Hibiki Omori, Toshihiro Oikawa, Katsunari Ohnuma, Ikuo Ishida, Kiyohito Kainuma, Ryosuke https://hdl.handle.net/11115/247 2015-09-24T02:19:58Z 2014-09-29T00:00:00Z

Phase equilibria and thermodynamic calculation of the CoeTa binary system Shinagawa, Kazuya; Chinen, Hibiki; Omori, Toshihiro; Oikawa, Katsunari; Ohnuma, Ikuo; Ishida, Kiyohito; Kainuma, Ryosuke Experimental investigation and thermodynamic evaluation of the CoeTa binary phase diagram was carried out. Equilibrium compositions obtained in two-phase alloys and diffusion couples were measured by electron probe microanalyzer (EPMA). A very narrow l3(C36) þ l2(C15) two-phase region is confirmed to be present around 26.5 at.% Ta at temperatures between 950 C and 1448 C. Equilibrium relationships above 1500 C among the liquid, Laves (l1(C14), l2 and l3, whose stoichiometry is described by Co2Ta), m(D8b) and CoTa2(C16) phases were investigated by microstructural examination in as-cast Co-(24-60 at.%)Ta alloys. The solvus temperature of the g0 Co3Ta (L12) phase precipitated in the 5.8 at.%Ta g(Co) and the peritectoid temperature of the Co7Ta2 phase in an 8.5 at.%Ta alloy were determined to be 1013 C and 1033 C, respectively, by differential scanning calorimeter (DSC). Fine precipitates of the g0 phase precipitated in the g (A1) matrix were observed by transmission electron microscope (TEM). Analyzing the present experimental results synthetically, the g0 Co3Ta phase was identified to be a metastable phase, of which the g/g0 transition temperature of the stoichiometric Co3Ta alloy was estimated to be 2000 C. Thermodynamic assessment of the CoeTa binary system was carried out based on the present results as well as on experimental data in the literature. Calculated results of not only stable but also metastable equilibria were found to be in good agreement with the revised phase diagram. The evaluated stability of the metastable g0 Co3Ta coincides with the enthalpy of formation (DH(g’,Co3Ta) = 23.44 kJ/mol) calculated by the ab initio method.

2014-09-29T00:00:00Z Lass, Eric Maureen E. Williams Carelyn E. Campbell Kil-Won Moon Ursula R. Kattner https://hdl.handle.net/11256/96 2017-02-02T03:42:40Z 2014-09-03T00:00:00Z

Al-Co-W 900C Phase Equilibria Data Lass, Eric; Maureen E. Williams; Carelyn E. Campbell; Kil-Won Moon; Ursula R. Kattner Phase equilibria at 900 °C in the Co-rich Co-Al-W ternary system are investigated through isothermal annealing of six alloy compositions for times up to 8000 h. The volume fraction of the L12-γ′ phase co-existing with disordered FCC-γ, B2 and D019 phases is found to steadily decrease with increasing annealing time indicating that it is unstable at 900 °C. Additional heat treatments at 850 and 1000 °C further suggest it is a nonequilibrium phase at all temperatures in the ternary system. The L12-γ′ phase dissolves slowly with significant amounts remaining in some alloys after 8000 h at 900 °C. However, the present work clearly indicates the microstructure is moving toward a three-phase equilibrium between γ, D019, and B2. The collected compositional and phase equilibria information provide much needed data for improving the available thermodynamic assessments of the ternary Co-Al-W alloy system.

2014-09-03T00:00:00Z