Nanoscale phase separation in metallic glasses studied by advanced electron microscopy techniques

Y. Hirotsu, T. Hanada, T. Ohkubo, A. Makino, Y. Yoshizawa, T. G. Nieh

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

To understand atomic structures of metallic glasses, advanced electron microscopy was employed to analyze local structures of some Fe-based and Zr-based metallic glasses. In the as-formed Fe70Nb10B 20 and Fe73.5Nb3Si13.5Cu 1B9 glasses, crystalline nano-clusters as small as 1 nm were observed using HREM (high resolution electron microscopy) under optimized defocus conditions. Nano-diffraction with a probe size of 1 nm revealed diffraction patterns of bcc-Fe and Fe-compound, suggesting the presence of nanoscale phase separation in these as-formed specimens. Atomic pair distribution function was calculated from analyzing electron diffraction intensity obtained from a large area in the samples using energy-filtering. For the Fe-Nb-B glass, an averaged atomic structural model with 2500 atoms was constructed using reverse Monte-Carlo calculation followed by Voronoi polyhedral analysis. The analysis revealed the presence of bcc-Fe-like, B-centered trigonal prism and highly coordinated Nb-Fe polyhedral structures, which was consistent with experimental results of HREM and nano-diffraction. A Zr 71Cu13Ni10Ti3Al3 bulk metallic glass was also studied using HREM and high angle annular dark-field (HAADF) techniques. Crystalline clusters with sizes of about 1-2 nm were detected in the as-cast Zr71Cu13Ni10Ti 3Al3. In the HAADF image, bright contrasts extending as small as 2 nm were found to fluctuate locally, indicating a local compositional fluctuation caused by nanoscale phase separation.

Original languageEnglish
Pages (from-to)1081-1088
Number of pages8
JournalIntermetallics
Volume12
Issue number10-11 SPEC. ISS.
DOIs
Publication statusPublished - 2004 Oct 1
Externally publishedYes

Keywords

  • B. Glasses, metallic
  • D. Microstructure
  • E. Simulations
  • F. Diffraction (electron, neutron and X-ray)
  • F. Electron microscopy, transmission
  • Monte Carlo

ASJC Scopus subject areas

  • Chemistry(all)
  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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