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Journal of Phase Equilibria and Diffusion

, Volume 27, Issue 5, pp 452–455 | Cite as

Evaluation of the invariant reactions in the Ta-rich region of the Ta-B system

  • Vanessa Motta Chad
  • Érika Coaglia Trindade Ramos
  • Gilberto Carvalho Coelho
  • Carlos Angelo Nunes
  • Paulo Atsushi Suzuki
  • Flávio Ferreira
  • Peter Rogl
Section I: Basic And Applied Research

Abstract

Invariant reactions in the Ta-rich side of the Ta-B system were evaluated. The alloys were arc melted from pure materials. Pellets prepared from powder mixtures of Ta and TaB were heat treated under vacuum at 1900 and 1950 °C. The microstructures of the alloys were characterized through scanning electron microscopy images and x-ray diffraction (XRD). The microstructural analyses confirmed the type of reactions occurring in Ta-rich region; however, the composition of the liquid phase should be altered: (a) L ↔ TaSS+Ta2B from 23 to 18 at.% B and (b) L+TaB↔Ta2B from 27 to 22.5 at.% B. The formation of Ta3B2 was confirmed as the understoichiometry of Ta2B. The decomposition of Ta2B occurs between 1900 and 1950 °C. The XRD data for alloys with composition between 34 and 50 at.% B indicate the existence of a new high-temperature phase.

Keywords

borides phase diagram Ta-B system 

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Copyright information

© ASM International 2006

Authors and Affiliations

  • Vanessa Motta Chad
    • 1
  • Érika Coaglia Trindade Ramos
    • 1
  • Gilberto Carvalho Coelho
    • 1
  • Carlos Angelo Nunes
    • 1
  • Paulo Atsushi Suzuki
    • 1
  • Flávio Ferreira
    • 2
  • Peter Rogl
    • 3
  1. 1.FAENQUIL, Departamento de Engenharia de Materiais (DEMAR)Polo Urbo-Industrial Gleba AI-6LorenaBrazil
  2. 2.UFF- Escola de Engenharia Industrial Metalúrgica de Volta Redonda—TMCVolta RedondaBrazil
  3. 3.Universität Wien, Institut für Physikalische ChemieWienAustria

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