Influence of Convection on Eutectic Microstructure

  • V. Baskaran
  • G. F. Eisa
  • W. R. Wilcox
Conference paper

Abstract

The composition field in front of a growing lamellar eutectic was determined numerically, both with and without a lateral convective flow. By minimization of the interfacial undercooling it was found that the lamellar spacing λ is a function of GuλO 2/D and We, where λO is the value of λ for Gu = 0, Gu is the transverse velocity gradient at the freezing interface, D is the diffusion coefficient in the melt, and We is the eutectic composition. The value of λ increases as stirring increases, especially at low freezing rates.

Experiments were performed on MnBi-Bi eutectic using spinup/spin-down to provide controlled convection. The value of λ was reduced significantly by the stirring. As predicted, λ increased with increasing radial position. Furthermore at low freezing rates, the morphology was dramatically altered by convection. With stirring at low freezing rates the manganese mass fraction increased with increasing radial position, and sometimes MnBi was missing entirely from the center.

This research was supported by NASA under contract NAS834887.

Keywords

Furnace Anisotropy Convection Manganese Bismuth 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Baskaran, V. (1983) M.S. Thesis, Clarkson College of Technology, Potsdam, New York.Google Scholar
  2. Greenspan, H.G. (1968) The Theory of Rotating Fluids. University Press, Cambridge, p. 31.MATHGoogle Scholar
  3. Jackson, K.A., and Hunt, J.D. (1966) Lamellar and Rod Eutectic Growth. Trans. AIME 236: 1129–1142.Google Scholar
  4. Pirich, R.G., and Larson, D.J. (1982) Influnce of Gravity Driven Convection on the Directional Solidification of Bi/ MnBi Eutectic Composites, pp. 523–532 in Materials Processing in the Reduced Gravity Environment of Space, ed. G.E. Rindone, Elsevier Science Publishing Co.Google Scholar
  5. Ravishankar, P.S., Wilcox, W.R., and Larson, D. (1980) The Microstructure of MnBi/Bi Eutectic Alloys. Acta Met. 28: 1583.CrossRefGoogle Scholar
  6. Wilcox, W.R., Doddi, K., Nair, M., and Larson, D.J. (1983) Influence of Freezing Rate Changes on MnBi-Bi Eutectic Microstructure. Adv. Space Res. 3: 79–83.Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1984

Authors and Affiliations

  • V. Baskaran
    • 1
  • G. F. Eisa
    • 1
  • W. R. Wilcox
    • 1
  1. 1.Department of Chemical EngineeringClarkson College of TechnologyPotsdamUSA

Personalised recommendations