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On the effect of Ti addition on microstructural evolution, precipitate coarsening kinetics and mechanical properties in a Co–30Ni–10Al–5Mo–2Nb alloy

Pandey, P and Shankar Prasad, A and Baler, N and Chattopadhyay, K (2021) On the effect of Ti addition on microstructural evolution, precipitate coarsening kinetics and mechanical properties in a Co–30Ni–10Al–5Mo–2Nb alloy. In: Materialia, 16 .

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Official URL: https://doi.org/10.1016/j.mtla.2021.101072


In this work, the effect of varying Ti content on the γ/γ' microstructure, precipitate coarsening kinetics, and mechanical properties in a series of Co-30Ni-10Al-5Mo-2Nb-xTi alloys (where x = 0, 1, 2, 3, and 4 at. %) is presented. An addition of 2 at. % Ti and beyond changes the γ′ morphology from rod shape (alloys containing 0 and 1 at. % Ti) to cuboidal shape (alloys containing 2 to 4 at% Ti) when aged beyond 500 h at 900 °C. The composition profiles obtained by STEM-EDS analysis reveal a strong partitioning of Ni, Ti, Al, and Nb in the γ′ precipitate, whereas partitioning of Mo changes from (KMo>1) γ′ precipitates for Co-30Ni-10Al-5Mo-2Nb alloy to equal proportion in both the phases (KMo∼1) for alloys containing 1 at.% Ti or more. Among the alloys studied, Co-30Ni-10Al-5Mo-2Nb-4Ti alloy exhibits an excellent combination of low mass density (8.19 g/cc) and high γ′ solvus temperature (1117 °C). The addition of Ti to the base 2Nb0Ti alloy introduces a 0.2% proof stress anomaly with temperature with a peak in strength was observed at 770 °C. The experimentally determined temporal evolution of average γ′ precipitate size suggests an LSW model-based evaporation-condensation (EV) coarsening mechanism in alloys containing 1 and 2 at% Ti. In contrast, a combined EV and coalescence/coagulation coarsening mechanisms operates in alloys with 3 and 4 at% Ti at the aging temperature of 900 °C. Despite the increase in γ/γ′ stability, the coarsening rate constant, calculated using modified LSW based coarsening model, increases by six times with an increase in Ti content from 1 to 4 at.%.

Item Type: Journal Article
Publication: Materialia
Publisher: Elsevier B.V.
Additional Information: The copyright for this article belongs to Elsevier B.V.
Keywords: Aluminum alloys; Cobalt alloys; Kinetics; Microstructural evolution; Molybdenum alloys; Niobium alloys; Ostwald ripening; Precipitation (chemical); Rate constants; Titanium alloys, Co-based superalloys; Coarsening kinetics; Evaporation-condensation; Low mass density; Mechanical; Partition coefficient; Precipitate coarsening; Property; Ti content; �� solvus temperature, Coarsening
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 13 Apr 2023 07:51
Last Modified: 13 Apr 2023 07:51
URI: https://eprints.iisc.ac.in/id/eprint/80605

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