Directional solidification microstructures in diffusive and convective regimes

R. Trivedi, Hirofumi Miyahara, P. Mazumder, E. Simsek, S. N. Tewari

Research output: Contribution to journalArticle

95 Citations (Scopus)

Abstract

Most theoretical models on the development of solidification microstructures are based on diffusive growth conditions, whereas convection effects are generally present in most directional solidification experiments. This paper examines the effect of convection on the development of microstructures in directionally solidified Al-Cu alloys. A numerical model of convection is first discussed to characterize fluid flow as a function of sample diameter for the thermal profile of the directional solidification used in this study, and it was established that sample diameters of 1 mm or smaller is required for diffusive growth. Based on this result, a new experimental design is developed for directionally solidifying several thin samples of different diameters in the same experimental run to systematically study the effect of sample diameter on microstructure development. Sample diameters, ranging from 0.2 to 5.0 mm, were used to access both the diffusive and convective regimes. Experiments have been performed over a range of velocities and temperature gradients to characterize the effect of convection on planar, cellular and dendritic microstructures. In very thin samples of ≤1.0 mm diameter, diffusive growth was obtained. The cell/dendrite tip composition and primary spacing were found to increase, and the tip temperature was found to decrease, as the convection effects were reduced in thinner samples. The planar to cellular transition was suppressed in the presence of fluid flow. Also, convection was found to slightly increase the critical velocity for cellular to dendritic transition.

Original languageEnglish
Pages (from-to)365-379
Number of pages15
JournalJournal of Crystal Growth
Volume222
Issue number1-2
DOIs
Publication statusPublished - Jan 1 2001

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Solidification
convection
microstructure
Microstructure
Flow of fluids
fluid flow
critical velocity
Design of experiments
Thermal gradients
dendrites
Convection
Numerical models
solidification
Experiments
temperature gradients
spacing
gradients
Chemical analysis
profiles
cells

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Inorganic Chemistry
  • Materials Chemistry

Cite this

Directional solidification microstructures in diffusive and convective regimes. / Trivedi, R.; Miyahara, Hirofumi; Mazumder, P.; Simsek, E.; Tewari, S. N.

In: Journal of Crystal Growth, Vol. 222, No. 1-2, 01.01.2001, p. 365-379.

Research output: Contribution to journalArticle

Trivedi, R. ; Miyahara, Hirofumi ; Mazumder, P. ; Simsek, E. ; Tewari, S. N. / Directional solidification microstructures in diffusive and convective regimes. In: Journal of Crystal Growth. 2001 ; Vol. 222, No. 1-2. pp. 365-379.
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