Enthalpy relaxation behaviour of Al-Si-Cr quasicrystalline and amorphous alloys upon annealing

A. Inoue, A. P. Tsai, H. M. Kimura, T. Masumoto

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8 Citations (Scopus)

Abstract

Annealing-induced enthalpy relaxation behaviour was examined calorimetrically in quasicrystalline Al62Si19Cr19 and amorphous Al60Si25Cr15 alloys. When both alloys annealed at temperatures below Tx are reheated, an excess endothermic reaction (enthalpy relaxation) occurs reversibly above the annealing temperature, Ta. The peak temperature of ΔCp,endo rises in a continuous manner with the logarithm of annealing time (ta). The magnitudes of ΔCp,endo and ΔHendo of the amorphous alloy increase with increasing Ta while no appreciable change in ΔCp,endo and ΔHendo of the quasicrystal with Ta is seen. The activation energy, Qm, for the enthalpy relaxation increases from 1.8 to 2.7 eV with the peak temperature of ΔCpTm, for the amorphous alloy, whereas it remains constant (≅1.3 eV) for the quasicrystal. The endothermic reaction with small Om for the quasicrystal is thought to be attributable to the disappearance of short-range ordering of chromium and silicon atoms with stronger attractive interaction, which developed during annealing, i.e. the reversion phenomenon, in the unrelaxed localized regions with high free-energy isolately embedded in the more stable icosahedral structure. The similarity of the enthalpy relaxation behaviour between the quasicrystalline and amorphous phases allows us to infer that short-range atomic configuration is very similar between the quasicrystalline and amorphous phases.

Original languageEnglish
Pages (from-to)429-437
Number of pages9
JournalJournal of Materials Science
Volume23
Issue number2
DOIs
Publication statusPublished - 1988 Feb 1

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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