Abstract
The work reported here concerns the effect of Si on the precipitation of θ′ phase (metastable Al2Cu) during the isothermal aging of Al-2Cu-1 Si (wt pct). The binary alloys Al-2Cu and Al-1 Si were studied for comparison. Only two precipitate phases were detected: essentially pure Si in Al-1 Si and Al-2Cu-1 Si, and θ′ (metastable Al2Cu) in Al-2Cu and Al-2Cu-1Si. On aging the ternary alloy at 225 °C, Si precipitates first and catalyzes the θ′ phase. The precipitates in the ternary alloy are smaller, are more densely distributed, have lower aspect ratios, and coarsen more slowly than those in the binary Al-2Cu aged at the same temperature. While the shapes of individual θ′ precipitates in binary Al-2Cu are strongly affected by the kinetic problem of nucleating growth ledges, which produces a significant scatter in the aspect ratio for samples of given thickness, the overall evolution of particle shape with size follows the predictions of the Khachaturyan-Hairapetyan (KH) thermoelastic theory, which reduces to κ=L/d ∞ √L at large sizes. The KH theory provides an estimate for the interfacial tension of the broad Al-θ′ interface of 85 to 96 mJ/m2, which is near the values for other low-energy interfaces in Al, such as the twin boundary energy (100 mJ/m2) and the antiphase boundary energy in δ′ Al3Li (70 mJ/m2). Si and θ′ precipitates in Al-2Cu-1 Si have a strong elastic interaction because of their compensating strain fields. This elastic interaction promotes the nucleation of θ′ precipitates on Si, decreases the expected aspect ratio of θ′, and inhibits coarsening. Finally, Si precipitation in ternary Al-2Cu-1 Si differs from that in binary Al-1 Si in that the Si precipitates are coarser, more equiaxed, and more extensively twinned. These changes appear to be effects of Cu, which increases the solubility of Si in Al and adsorbs on the Si-Al interface, promoting twinning by a “step-poisoning” effect at the interface.
Similar content being viewed by others
References
J.W. Morris, Jr., C.-U. Kim, and S.H. Kang: J. Met., 1996, vol. 48, pp. 43–46.
C.-U. Kim, S.I. Selitser, and J. W. Morris, Jr.: J. Appl. Phys., 1994, vol. 75, pp. 879–84.
J.H. Han, M.C. Shin, S.J. Kang, and J.W. Morris, Jr.: Appl. Phys. Lett., 1998, vol. 73, pp. 762–64.
E.G. Colgan and K.P. Rodbell: J. Appl. Phys., 1994, vol. 75, pp. 3423–34.
S.H. Kang and J.W. Morris, Jr.: J. Kor. Phys. Soc, 1999, vol. 35, p. 412–18.
D.A. Porter and K.E. Easterling: Phase Transformations in Metals and Alloys, 2nd ed., Chapman and Hall, London, 1992, pp. 291–302.
M.J. Starink and P. Van Mourik: Metall. Trans. A, 1991, vol. 22A, pp. 665–74.
M.J. Starink and P. Van Mourik: J. Mater. Sci., 1994, vol. 29, pp. 2835–40.
A.T. Steward and J.W. Martin: J. Inst. Met., 1970, vol. 96, pp. 62–63.
S.P. Ringer, K. Hono, I.J. Polmear, and T. Sakurai: Acta Metall., 1996, vol. 44, pp. 1883–98.
R.N. Wilson: J. Inst. Met., 1969, vol. 97, pp. 80–86.
V. Radmilovic, G. Thomas, G.J. Shiflet, and E.A. Starke: Scripta Metall., 1989, vol. 23 pp. 1141–46.
S.K. Das, G. Thomas, and D. Rowcliffe: Proc. 7th Int. Conf. Electron Microscopy, Grenoble, France, Soc. Francaise de Microscopic, Paris, France, 1970, pp. 533–34.
S.P. Ringer, K. Hono, and T. Sakurai: Metall. Mater. Trans. A, 1995, vol. 26A, pp. 2207–18.
I. Dutta, S.M. Allen, and J.L. Hafley: Metall. Trans., 1991, vol. 22A, pp. 2553–63.
T. Christman and S. Suresh: Acta Metall., 1988, vol. 36, pp. 1691–04.
G.J. Mahan, J.M. Howe, and A.K. Vasudevan: Acta Metall. Mater., 1990, vol. 38, pp. 1503–12.
G. Thomas and M.J. Whelan: Phil. Mag., 1959, vol. 4, pp. 511–27.
A.G. Khachaturyan: Theory of Structural Transformations in Solids, John Wiley and Sons, New York, NY, 1983, ch. 8.
R.D. Doherty: in Physical Metallurgy, R.W. Cahn and P. Haasen, eds., North-Holland, Amsterdam, 1996, pp. 1405–21.
J.D. Boyd and R.B. Nicholson: Acta Metall., 1971, vol. 19, pp. 1101–09 and 1379–91.
R. Sankaran and C. Laird: Acta Metall., 1974, vol. 22, pp. 957–69.
R. Sankaran and C. Laird: Scripta Metall., 1977, vol. 11, pp. 383–86.
G.J. Shiflet, H.I. Aaronson, and T. Courtney: Scripta Metall., 1977, vol. 11, pp. 677–80.
P. Merle and F. Fouquet: Acta Metall., 1981, vol. 29, pp. 1919–27.
P. Merle and J. Merlin: Acta Metall., 1981, vol. 29, pp. 1929–38.
P. Merle and R.D. Doherty: Scripta Metall., 1982, vol. 16, pp. 357–60.
B.D. Cullity: Elements of X-Ray Diffraction, 2nd ed., Addison-Wesley Publishing Company, Inc., New York, NY, 1978, pp. 506–07.
J.M. Silcock, T.J. Heal, and H.K. Hardy: J. Inst. Met., 1953–54, vol. 82, pp. 1519–2148.
A. Saulinier: Mem. Sci. Rev. Metall., 1961, vol. 58, pp. 615–25.
H.S. Rosenbaum and D. Turnbull: Acta Metall., 1958, vol. 6, pp. 654–59.
H.S. Rosenbaum and D. Turnbull: Acta Metall., 1959, vol. 7, pp. 664–74.
H.S. Rosenbaum and D. Turnbull: Acta Metall., 1959, vol. 7, pp. 678–79.
S. Hinderberger, S.-Q. Xiao, K.H. Westmacott, and U. Dahmen: Z. Metallkd., 1996, vol. 87, pp. 161–70.
J. Douin, U. Dahmen, and K.H. Westmacott: Phil. Mag. B, 1991, vol. 63, pp. 867–90.
S.Q. Xiao, S. Hindenberger, K.H. Westmacott, and U. Dahmen: Phil. Mag. B, 1996, vol. 73, pp. 1261–78.
G.R. Hugo and B.C. Muddle: Acta Metall. Mater., 1990, vol. 38, pp. 351–63.
P. Hirsch, A. Howie, R.B. Nicholson, D.W. Pashley, and M.J. Whelan: Electron Microscopy of Thin Crystals, Robert E. Krieger Publishing Co., Malabar, Florida, 1977, pp. 317–27 and 415–22.
A.G. Khachaturyan and V.G. Hairapetyan: Phys. Status Solidi B, 1973, vol. 57, pp. 801–07.
J.W. Morris, Jr., A.G. Khachaturyan, and S.H. Wen: Proc. NATO Advanced Study Institute in Modulated Structure Materials, T. Tsakalakos, ed., Martinus Nijhoff, Dordrecht, Holland, 1984, pp. 32–46.
Landolt-Bornstein LBIII/29a—Low Frequency Properties of Dielectric Crystals: Second and Higher-Order Elastic Constants, D.F. Nelson, ed., Springer-Verlag, Berlin, 1992.
H.B. Huntington: Solid State Phys., 1958, vol. 7, p. 213.
H.I. Aaronson, J.B. Clark, and C. Laird: Met. Sci. J., 1968, vol. 2, p. 155 (cited by Sankaran and Laird[23]).
J.P. Hirth and J. Lothe: Theory of Dislocations, 2nd ed., Krieger Publishing, Malabar, FL, 1982, Appendix 2
A.G. Khachaturyan and J.W. Morris, Jr.: Phil. Mag., 1987, vol. 56, pp. 517–32.
T.B. Massalski: in Binary Alloy Phase Diagrams, J.L. Murray, L.H. Bennett, and H. Baker, eds., ASM, Metals Park, OH, 1986, pp. 106–07 and 164–65.
Handbook of Ternary Alloy Phase Diagrams, P. Villars, A. Prince, and H. Okamoto, eds., ASM, Metals Park, OH, 1995, vol. 3. pp. 3331–50.
N. Cabrera and D.A. Vermilyea: Growth and Perfection of Crystals, Wiley, New York, NY, 1958, p. 394.
S.-Z. Lu and A. Hellawell: Metall. Trans. A, 1987, vol. 18A, pp. 1721–33.
Mark McCormack, A.G. Khachaturyan, and J.W. Morris, Jr.: Acta Metall. Mater., 1992, vol. 40, pp. 325–31.
K. Thornton, N. Akaiwa, and P.W. Voorhees: in Phase Transformations and Evolution in Materials, P.E.A. Turchi and A. Gonis, eds., TMS, Warrendale, PA, 2000, pp. 73–88.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Mitlin, D., Morris, J.W. & Radmilovic, V. Catalyzed precipitation in Al-Cu-Si. Metall Mater Trans A 31, 2697–2711 (2000). https://doi.org/10.1007/BF02830329
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF02830329