Metallurgical and Materials Transactions A

, Volume 30, Issue 2, pp 449–455 | Cite as

A new hot-tearing criterion

  • M. Rappaz
  • J. -M. Drezet
  • M. Gremaud
Article

Abstract

A new criterion for the appearance of hot tears in metallic alloys is proposed. Based upon a mass balance performed over the liquid and solid phases, it accounts for the tensile deformation of the solid skeleton perpendicular to the growing dendrites and for the induced interdendritic liquid feeding. This model introduces a critical deformation rate (\(\dot \varepsilon _{p,\max } \)) beyond which cavitation, i.e., nucleation of a first void, occurs. As should be expected, this critical value is an increasing function of the thermal gradient and permeability and a decreasing function of the viscosity. The shrinkage contribution, which is also included in the model, is shown to be of the same order of magnitude as that associated with the tensile deformation of the solid skeleton. A hot-cracking sensitivity (HCS) index is then defined as \(\dot \varepsilon _{_{p,\max } }^{ - 1} \). When applied to a variable-concentration aluminum-copper alloy, this HCS criterion can reproduce the typical “Λ curves” previously deduced by Clyne and Davies on a phenomenological basis. The calculated values are in fairly good agreement with those obtained experimentally by Spittle and Cushway for a non-grain-refined alloy. A comparison of this criterion to hot cracks observed in ring-mold solidification tests indicates cavitation depression of a few kilo Pascal and tensile stresses in the coherent mushy zone of a few mega Pascal. These values are discussed in terms of those obtained by other means (coherency measurement, microporosity observation, and simulation). Even though this HCS criterion is based only upon the appearance of a first void and not on its propagation, it sets up for the first time a physically sound basis for the study of hot-crack formation.

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References

  1. 1.
    W. Kurz and D.J. Fisher: Fundamentals of Solidification, 3rd ed., Trans Tech Publications, Aedermannsdorf, Switzerland, 1989.Google Scholar
  2. 2.
    J. Campbell: Castings, Butterworth-Heinemann, Oxford, United Kingdom, 1991.Google Scholar
  3. 3.
    T.S. Piwonka and M.C. Flemings: Trans. AIME, 1966, vol. 236, pp. 1157–65.Google Scholar
  4. 4.
    K. Kubo and R.D. Pehlke: Metall. Trans. B, 16B (1985) 359–66.Google Scholar
  5. 5.
    J. Ampuero, Ch. Charbon, A.F.A. Hoadley, and M. Rappaz: in Materials Processing in the Computer Age, V.R. Voller, M.S. Stachowicz, and B.G. Thomas, eds., TMS, Warrendale, PA, 1991, pp. 377–88.Google Scholar
  6. 6.
    T.W. Clyne and G.J. Davies: Br. Foundryman, 1981, vol. 74, pp. 65–73; Br. Foundryman, 1975, vol. 68, pp. 238–44.Google Scholar
  7. 7.
    F. Matsuda, H. Nakagawa, S. Katayama, and Y. Arata: Trans. Jpn. Weld. Soc. 13 (1982) 115–32; Trans. Welding Res. Inst., Osaka Univ. 6 (1977) 197–206; Trans. Welding Res. Inst., Osaka Univ., 5 (1976) 135–51.Google Scholar
  8. 8.
    U. Feurer: Giesserei Forsch., 2 (1976) 75–80.Google Scholar
  9. 9.
    R. Jauch: Stahl Eisen 98 (1978) 244–54.Google Scholar
  10. 10.
    T.W. Clyne, M. Wolf, and W. Kurz: Metall. Trans. B, 13B (1982) 259–66.Google Scholar
  11. 11.
    Y.F. Guven and J.D. Hunt: Cast Met., 1 (1988) 104–11.Google Scholar
  12. 12.
    D. Warrington and D.G. McCartney: Cast Met., 2 (1989) 134–143.Google Scholar
  13. 13.
    J. Campbell and T.W. Clyne: Cast Met., 3 (1991) 224–26.Google Scholar
  14. 14.
    J.-M. Drezet and M. Rappaz: in Modeling of Casting, Welding and Advanced Solidification Processes VIII, B.G. Thomas, C. Beckermann, and I. Ohnaka, eds., TMS, Warrendale, PA, 1998, pp. 883–90.Google Scholar
  15. 15.
    Guocai Chai: Ph.D. Thesis, Chem. Communic., Stockholm, 1994, No 1.Google Scholar
  16. 16.
    P. Vicente: Ph.D. Thesis, Ecole Nationale Supérieure des Mines de Paris, Paris, 1994.Google Scholar
  17. 17.
    P. Ackermann, W. Kurz, and W. Heinemann: Mater. Sci. Eng., 75 (1985) 79–86.CrossRefGoogle Scholar
  18. 18.
    W. Kurz: private communication, Ecole Polytechnique Fédérale de Lausanne, Switzerland, 1996.Google Scholar
  19. 19.
    H. Esaka, W. Kurz, and R. Trivedi: in Solidification Processing, J. Beech and H. Jones, eds., Institute of Metals, London, 1988, pp. 198–201.Google Scholar
  20. 20.
    C.Y. Wang and C. Beckermann: Metall. Trans. A, 24A (1993) 2787–2802.Google Scholar
  21. 21.
    E. Niyama, T. Uchida, M. Morikawa, and S. Saito: AFS Int. Cast Met. J., 1982, Sept., pp. 52–63.Google Scholar
  22. 22.
    J.A. Spittle and A.A. Cushway: Met. Technol., 1983, vol. 10, pp. 6–13.Google Scholar
  23. 23.
    P. Rousset, M. Rappaz, and B. Hannart: Metall. Trans. A, 1995, vol. 26A, pp. 2349–58.Google Scholar

Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 1999

Authors and Affiliations

  • M. Rappaz
    • 1
  • J. -M. Drezet
    • 1
  • M. Gremaud
    • 2
  1. 1.the Laboratoire de Métallurgie PhysiqueEcole Polytechnique Fédérale de LausanneLausanneSwitzerland
  2. 2.Calcom SALausanneSwitzerland

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