Abstract
Decomposition of nickel-base alloys by precipitation of the γ′ phase occurs either continuously (homogeneously) or discontinuously. Under certain conditions of solute content and temperature, discontinuous precipitation is observed. Ni-Al-Co alloys have been characterized by coupling atom probe tomography with transmission electron microscopy studies. The primary focus was to investigate the discontinuous precipitation of γ and γ′ phases. When subjected to fast quenching after solution treatment, the γ′ precipitates exhibit a near-spherical shape and monomodal size distribution with an average size of less than 5 nm. After early stage annealing at 600°C for 10 min, discontinuous precipitation nucleated near the grain boundaries while some regions of homogeneous γ′ precipitates were observed. Discontinuous γ + γ′ product was completely transformed throughout the grain after 600°C/1 h. On long-term annealing (600°C/256 h), coarser γ + γ′ lamellae products replaced the fine discontinuous products that exhibited after 1 h annealing at 600°C. Equilibrium compositions of the γ and γ′ phases were achieved in this coarsening stage. The γ′ phase has an Al content of 25 at.%, which is consistent with the as-quenched condition where the (Ni + Co)3Al stoichiometry is maintained after 600°C/256 h annealing.
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References
T. Chuang, R. Fournelle, W. Gust, and B. Predel, Acta Metall. 36, 775 (1988).
G. Geber, Appl. Surf. Sci. 87, 234 (1995).
W. Gust, B. Predel, and S.N. Mehra, Mater. Sci. Eng. 21, 131 (1975).
S. Lee, K. Lee, and T. Chuang, Mater. Sci. Eng. A 251, 135 (1998).
P. Ziȩba, G. Cliff, and G.W. Lorimer, Acta Mater. 45, 2093 (1997).
R. Williams, Trans. TMS-AIME 215, 1026 (1959).
C. Davies, P. Nash, and R. Stevens, J. Mater. Sci. 15, 1521 (1980).
C. Davies, P. Nash, R. Stevens, and L. Yap, J. Mater. Sci. 20, 2945 (1985).
J. Nystrom, T. Pollock, W. Murphy, and A. Garg, Metall. Mater. Trans. A 28, 2443 (1997).
W. Hagel and H. Beattie Jr., Trans. Met. Soc. AIME 215 (1959).
W. Betteridge and J. Heslop, The Nimonic Alloys and Other Nickel-Base High-Temperature Alloys (London, UK: Edward Arnold Publishers Ltd., 1974).
R.C. Reed, The Superalloys: Fundamentals and Applications (Cambridge, UK: Cambridge University Press, 2006).
D.P. Mourer, E.S. Huron, D.G. Backman, K.R. Bain, P.L. Reynolds, J.J. Schirra, and T.P. Gabb, Ni Based Superalloy and its use as Gas Turbine Disks, Shafts, and Impellers, European patent EP1195446 A1 (General Electric Company, 2002).
R. Kainuma, M. Ise, C. Jia, H. Ohtani, and K. Ishida, Intermetallics 4, S151 (1996).
J. Hwang, S. Nag, A. Singh, R. Srinivasan, J. Tiley, H. Fraser, and R. Banerjee, Scr. Mater. 61, 92 (2009).
J. Hwang, S. Nag, A. Singh, R. Srinivasan, J. Tiley, G. Viswanathan, H. Fraser, and R. Banerjee, Metall. Mater. Trans. A 40, 3059 (2009).
S. Baumann, J. Michael, and D. Williams, Acta Metall. 29, 1343 (1981).
R. Fournelle and J. Clark, Metall. Trans. 3, 2757 (1972).
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Rojhirunsakool, T., Nag, S. & Banerjee, R. Discontinuous Precipitation of γ′ Phase in Ni-Co-Al Alloys. JOM 66, 1465–1470 (2014). https://doi.org/10.1007/s11837-014-0998-8
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DOI: https://doi.org/10.1007/s11837-014-0998-8