Evolution of gamma/gamma-prime Microstructure in Ternary Co-Al-W Alloys

Published

June 29, 2015

Author(s)

Eric Lass, Yaakov S. Idell, Carelyn E. Campbell, Ursula R. Kattner

Abstract

The discovery of a two-phase γ (FCC)-γ' (L12) field in the ternary Co-Al-W phase diagram has sparked significant research interest into possible Co-based analogs to traditional Ni-based superalloys used in turbine engine applications. This work experimentally investigates microstructural evolution ternary Co-Al-W alloys. Nucleation of ordered γ' precipitates 2 nm to 10 nm in diameter cannot be suppressed even under rapid solidification conditions. Upon subsequent annealing, growth of these nuclei into irregular, non-cube shaped precipitates is very rapid, resulting in a volume fraction of γ' roughly equal to that in metastable equilibrium with the γ phase after only a few minutes. The microstructure then slowly coarsens to reveal the familiar cuboidal γ-γ' microstructure similar to that found in Ni-based superalloys. The two-phase microstructure is ultimately destroyed by the nucleation and growth of the additional phases Co3W (D019) indicating γ' is metastable in ternary Co-Al-W.

Proceedings Title

PTM 2015: International Conference on Solid-Solid Phase Transformations in Inorganic Materials, Conference Proceedings

Conference Dates

June 28-July 3, 2015

Conference Location

Whistler

Conference Title

PTM 2015: International Conference on Solid-Solid Phase Transformations in Inorganic Materials

Pub Type

Conferences

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Keywords

Co-based, superalloy, phase equilibrium

Citation

Lass, E. , Idell, Y. , Campbell, C. and Kattner, U. (2015), Evolution of gamma/gamma-prime Microstructure in Ternary Co-Al-W Alloys, PTM 2015: International Conference on Solid-Solid Phase Transformations in Inorganic Materials, Conference Proceedings, Whistler, -1, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=918086 (Accessed October 10, 2025)