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The role of Ti addition on the evolution and stability of γ/γ� microstructure in a Co-30Ni-10Al-5Mo-2Ta alloy

Mukhopadhyay, S and Pandey, P and Baler, N and Biswas, K and Makineni, SK and Chattopadhyay, K (2021) The role of Ti addition on the evolution and stability of γ/γ� microstructure in a Co-30Ni-10Al-5Mo-2Ta alloy. In: Acta Materialia, 208 .

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Official URL: https://doi.org/10.1016/j.actamat.2021.116736


The paper explores the influence of Ti addition to the Ta stabilized γ/γ� two-phase Co-based superalloys having the compositions of Co-30Ni-10Al-5Mo-2Ta-xTi (x = 0, 1, 2 and 4 at.). The microstructure of the alloys after solutionizing (1300 °C for 25 h) and quenching show fine distribution of γ� precipitates with spherical shape within the γ matrix. Aging of these alloys at 900 °C results in a morphological transition from spheroidal to cuboidal with a concomitant increase in γ/γ� lattice misfit as compared to the solutionized alloys. However, the γ/γ� lattice misfit of cuboidal particles decreases with an increase in Ti in the alloys. Atomic-scale compositional analysis by atom probe tomography across γ/γ� interface for the aged alloys indicates a preferential partitioning of Ti to the γ�. This can be correlated with the observed increase in the γ� solvus temperature up to 1166 °C for alloys with 4 at. Ti addition. The increase in Ti content also decreases the partitioning of Mo to the γ�. Despite the rise in solvus temperature, the coarsening study reveals an escalation in the γ� coarsening rate at 900 and 950 °C with a maximum for the alloy containing the highest Ti content. The initial stages of γ� coarsening follow diffusion-controlled LSW kinetics. However, during later stages, a propensity for particle coalescence could be observed. An addition of 3 and 4 at. Ti is shown to improve the high-temperature strength with 0.2 proof stress at 1000 °C of 360 and 400 MPa, respectively. © 2021 Acta Materialia Inc.

Item Type: Journal Article
Publication: Acta Materialia
Publisher: Acta Materialia Inc
Additional Information: The copyright for this article belongs to Acta Materialia Inc
Keywords: Aluminum alloys; Coarsening; Cobalt alloys; Molybdenum alloys; Ostwald ripening; Tantalum alloys, 0.2 Proof stress; Atom probe tomography; Co-based superalloys; Compositional analysis; Diffusion controlled; High temperature strength; Morphological transitions; Solvus temperature, Titanium alloys
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 17 Mar 2021 10:28
Last Modified: 17 Mar 2021 10:28
URI: http://eprints.iisc.ac.in/id/eprint/68398

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