Crystallization and fracture behavior of the Zr65- xAl7.5Cu17.5Ni10Six bulk amorphous alloys

J. S.C. Jang, Y. W. Chen, L. J. Chang, H. Z. Cheng, C. C. Huang, C. Y. Tsau

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Abstract

The crystallization behavior of amorphous Zr65- xAl7.5Cu17.5Ni10Six alloys, x=0-10, was studied by means of differential scanning calorimetry, X-ray diffractometry, and TEM. The calculated Trg (T g/T1) for these amorphous alloys increases with increasing silicon content from 0.55 to 0.60, which indicates that the silicon addition, could improve the GFA for the Zr65-xAl 7.5Cu17.5Ni10Six alloys. The activation energy of crystallization of the alloy 4Si was about 365 ± 5 kJ mol-1, both determined by the Kissinger and Avrami plot. This value is about 20% higher than the base alloy (314 kJ mol-), which implies that the silicon addition can increase the thermal stability for the Zr-based alloy. The average value of the Avrami exponent n were calculated to be 1.7-2.5 for the alloys in this study. In addition, the cube of crystal size as a function of isothermal annealing time presents a linear relationship for the Zr61Al7.5Cu17.5Ni10Si 4 alloy During isothermal annealing the Zr61Al 7.5Cu17.5Ni10Si4 alloy at 698 K, the Zr2Cu crystal with average size of 105 nm was first observed at the early stage (30% crystallization ratio) of crystallization. In addition, both nano-crystals of the ZrCu (∼100nm) and the Zr3Al (∼30nm) were also observed to precipitate from the amorphous matrix upon the middle stage (50% crystallization ratio) of crystallization. The fracture surface presents typical ductile vein pattern for 4Si amorphous alloy ribbon after bended to 180°. However, a ductile-brittle transition phenomenon occurs at the amorphous ribbon after 50% crystallization ratio of isothermal annealing at the temperature between Tg and Tx.

Original languageEnglish
Pages (from-to)122-129
Number of pages8
JournalMaterials Chemistry and Physics
Volume89
Issue number1
DOIs
StatePublished - 15 Jan 2005

Keywords

  • Bulk amorphous
  • Crystallization kinetics
  • Fracture behavior
  • Glass transition temperature
  • Zirconium-based alloy

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