Periodic structural fluctuations during the solidification of aluminum alloys studied by neutron diffraction

N. Iqbal, N. H. van Dijk, V. W.J. Verhoeven, T. Hansen, L. Katgerman, G. J. Kearley

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Time-resolved neutron diffraction measurements have been carried out to study the crystallization dynamics during the liquid-solid phase transformation in an Al-0.3Ti-0.02B (wt.%) alloy. Starting from the liquid phase, the temperature was reduced to below the thermodynamic transition temperature of T0=933 K by continuous cooling at rates of 0.6 and 0.06 K/min and by step-wise cooling in temperature steps of 1 K. After nucleation of the solid phase on the micron-size TiB2 particles in the liquid alloy, pronounced fluctuations in the Bragg-peak intensity of the growing crystallites are observed during solidification. These fluctuations have been analyzed by a time- correlation function to extract the frequency and correlation time of the fluctuations. The deduced correlation time and oscillation frequency strongly depend on the cooling rate. The correlation time increases and the oscillation frequency decreases for decreasing cooling rate. For step-wise cooling a monotonic increase in correlation time is observed for decreasing temperatures demonstrating a slowdown of the dynamics during the liquid to solid phase transformation.

Original languageEnglish
Pages (from-to)82-88
Number of pages7
JournalMaterials Science and Engineering A
Volume367
Issue number1-2
DOIs
Publication statusPublished - 25 Feb 2004
Externally publishedYes

Fingerprint

Neutron diffraction
aluminum alloys
solidification
Solidification
neutron diffraction
Aluminum alloys
Cooling
cooling
solid phases
Liquids
Phase transitions
phase transformations
oscillations
Crystallization
liquid alloys
Crystallites
Temperature
Superconducting transition temperature
liquids
Nucleation

Keywords

  • Aluminum alloy
  • Neutron diffraction
  • Solidification
  • Time-correlation

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Periodic structural fluctuations during the solidification of aluminum alloys studied by neutron diffraction. / Iqbal, N.; van Dijk, N. H.; Verhoeven, V. W.J.; Hansen, T.; Katgerman, L.; Kearley, G. J.

In: Materials Science and Engineering A, Vol. 367, No. 1-2, 25.02.2004, p. 82-88.

Research output: Contribution to journalArticle

Iqbal, N. ; van Dijk, N. H. ; Verhoeven, V. W.J. ; Hansen, T. ; Katgerman, L. ; Kearley, G. J. / Periodic structural fluctuations during the solidification of aluminum alloys studied by neutron diffraction. In: Materials Science and Engineering A. 2004 ; Vol. 367, No. 1-2. pp. 82-88.
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AU - Katgerman, L.

AU - Kearley, G. J.

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AB - Time-resolved neutron diffraction measurements have been carried out to study the crystallization dynamics during the liquid-solid phase transformation in an Al-0.3Ti-0.02B (wt.%) alloy. Starting from the liquid phase, the temperature was reduced to below the thermodynamic transition temperature of T0=933 K by continuous cooling at rates of 0.6 and 0.06 K/min and by step-wise cooling in temperature steps of 1 K. After nucleation of the solid phase on the micron-size TiB2 particles in the liquid alloy, pronounced fluctuations in the Bragg-peak intensity of the growing crystallites are observed during solidification. These fluctuations have been analyzed by a time- correlation function to extract the frequency and correlation time of the fluctuations. The deduced correlation time and oscillation frequency strongly depend on the cooling rate. The correlation time increases and the oscillation frequency decreases for decreasing cooling rate. For step-wise cooling a monotonic increase in correlation time is observed for decreasing temperatures demonstrating a slowdown of the dynamics during the liquid to solid phase transformation.

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