Metallurgical Transactions A

, Volume 21, Issue 1, pp 231–239 | Cite as

The influence of buoyant forces and volume fraction of particles on the particle pushing/entrapment transition during directional solidification of Al/SiC and Al/graphite composites

  • Doru M. Stefanescu
  • Avijit Moitra
  • A. Sedat Kacar
  • Brij K. Dhindaw


Directional solidification experiments in a Bridgman-type furnace were used to study particle behavior at the liquid/solid interface in aluminum metal matrix composites. Graphite or siliconcarbide particles were first dispersed in aluminum-base alloysvia a mechanically stirred vortex. Then, 100-mm-diameter and 120-mm-long samples were cast in steel dies and used for directional solidification. The processing variables controlled were the direction and velocity of solidification and the temperature gradient at the interface. The material variables monitored were the interface energy, the liquid/particle density difference, the particle/liquid thermal conductivity ratio, and the volume fraction of particles. These properties were changed by selecting combinations of particles (graphite or silicon carbide) and alloys (Al-Cu, Al-Mg, Al-Ni). A model which considers process thermodynamics, process kinetics (including the role of buoyant forces), and thermophysical properties was developed. Based on solidification direction and velocity, and on materials properties, four types of behavior were predicted. Sessile drop experiments were also used to determine some of the interface energies required in calculation with the proposed model. Experimental results compared favorably with model predictions.


Metallurgical Transaction Buoyant Force Critical Velocity Planar Interface Gravity Vector 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



interatomic distance


volume fraction of particles


acceleration due to gravity


thermal conductivity of particle


thermal conductivity of liquid


coefficient, function of type of repulsive forces acting between particle and solid


radius of particle


force acting on particle


drag force


repulsive force


constant in Neumann’s equation


growth velocity


critical growth velocity


viscosity of melt


relative viscosity


density difference between the particle and the liquid


density of liquid


density of particle


surface energy between solid and liquid


surface energy between liquid and vapor


surface energy between particle and liquid


surface energy between particle and solid


surface energy between particle and vapor


wetting angle


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    P.K. Rohatgi, R. Asthana, and S. Das:Int. Met. Rev., 1988, vol. 31 (3), pp. 115–39.Google Scholar
  2. 2.
    K.C. Russell, J. A. Cornie, and S. Y. Oh:Interfaces in Metal Matrix Composites, Proc. TMS Symp., A.K. Dhingra and S.G. Fishman, eds., TMS, Warrendale, PA, 1986, pp. 61–91.Google Scholar
  3. 3.
    B.K. Dhindaw, A.S. Kacar, and D.M. Stefanescu:Advanced Materials and Processing Techniques for Structural Applications, ASM Europe Conf., Paris, 1987, pp. 491–500.Google Scholar
  4. 4.
    D.M. Stefanescu, B.K. Dhindaw, A.S. Kacar, and A. Moitra:Metall. Trans. A, 1988, vol. 19A, pp. 2847–55.Google Scholar
  5. 5.
    D.M. Stefanescu and B.K. Dhindaw:Metals Handbook, ASM INTERNATIONAL, Metals Park, OH, 1988, vol. 15, pp. 142–47.Google Scholar
  6. 6.
    P.K. Rohatgi, F.M. Yarandy, and Y. Liu:Cast Reinforced Metal Composites, ASM INTERNATIONAL Conf. Proc., S.G. Fishman and A.K. Dhingra, eds., 1988, pp. 249–55.Google Scholar
  7. 7.
    M.W. Barsoum and P.D. Oronby:Surfaces and Interfaces in Ceramic Metal Systems, J. Pask and A. Evans, eds., Plenum Press, New York, NY, 1981, pp. 457–66.Google Scholar
  8. 8.
    S.K. Rhee:J. Am. Ceram. Soc, 1972, vol. 55 (6), pp. 300–02.CrossRefGoogle Scholar
  9. 9.
    J.T. Kristiansen, J.B. Borradaile, H. Westengen, A. Nygard, and D.O. Karlsen:Cast Reinforced Metal Composites, ASM INTERNATIONAL Conf. Proc., S.G. Fishman and A.K. Dhingra, eds., 1988, pp. 71–75.Google Scholar
  10. 10.
    G.H. Geiger and D.R. Poirier:Transport Phenomena in Metallurgy, Addison-Wesley Publishing Co., Reading, MA, 1973, pp. 18–70.Google Scholar
  11. 11.
    D.G. Thomas:J. Colloid Sci., 1965, vol. 20, pp. 267–77.CrossRefGoogle Scholar
  12. 12.
    W. Kurz and D.J. Fisher:Fundamentals of Solidification, Trans Tech Publications Ltd., Aedermannsdorf, Switzerland, 1986, p. 240.Google Scholar
  13. 13.
    A.W. Neumann, R.J. Good, C.J. Hope, and M. Sejpal:J. Colloid Interface Sci., 1974, vol. 69 (2), pp. 291–302.CrossRefGoogle Scholar
  14. 14.
    S.N. Omenyi and A.W. Neumann:J. Appl. Phys., 1976, vol. 47 (9), pp. 3956–62.CrossRefGoogle Scholar
  15. 15.
    L.E. Murr:Interfacial Phenomena in Metals and Alloys, Addison-Wesley Publishing Co., Reading, MA, 1975, p. 124.Google Scholar

Copyright information

© The Metallurgical of Society of AIME 1990

Authors and Affiliations

  • Doru M. Stefanescu
    • 1
  • Avijit Moitra
    • 1
  • A. Sedat Kacar
    • 1
  • Brij K. Dhindaw
    • 2
  1. 1.Solidification Laboratory, Department of Metallurgical and Materials EngineeringThe University of AlabamaTuscaloosa
  2. 2.I.I.T. KharagpurIndia

Personalised recommendations