The effect of zirconium on the omega phase in Ti-24Nb-[0–8]Zr (at.%) alloys

E. L. Pang, E. J. Pickering, S. I. Baik, David N Seidman, N. G. Jones*

*Corresponding author for this work

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Ti-Nb based β-Ti alloys are a promising new class of superelastic, shape-memory, and low-modulus materials for a wide range of applications. A critical phase in β-Ti alloys is the ω phase, which greatly affects the mechanical properties and superelastic/shape-memory behaviour of these materials. Zirconium, an important alloying constituent in many β-Ti alloys, is generally regarded as an ω suppressant, but the body of evidence supporting this view is unconvincing and includes a number of conflicting reports. In this article, the role of Zr on ω phase formation in Ti-Nb alloys is clarified using X-ray diffraction, transmission electron microscopy, and atom-probe tomography. Zirconium additions were found to suppress the formation of athermal ω phase upon quenching from high temperature. However, up to 8 at.% Zr additions to a Ti-24 at.% Nb alloy had little effect on the formation of isothermal ω phase following aging at 300 °C after 100 h. Furthermore, the isothermal ω precipitates were found to be strongly depleted in Nb but only weakly depleted in Zr. These results challenge the belief that Zr suppresses isothermal ω formation in β-Ti alloys, a result that is likely to be applicable beyond the Ti-Nb system considered here and information that can be used to assist in the design of future β-Ti alloys.

Original languageEnglish (US)
Pages (from-to)62-70
Number of pages9
JournalActa Materialia
Volume153
DOIs
StatePublished - Jul 1 2018

Fingerprint

Zirconium
Shape memory effect
Alloying
Tomography
Precipitates
Quenching
Aging of materials
Transmission electron microscopy
X ray diffraction
Atoms
Mechanical properties

Keywords

  • Atom-probe tomography
  • Omega phase
  • TEM
  • Ti-Nb
  • Zirconium

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

Cite this

Pang, E. L. ; Pickering, E. J. ; Baik, S. I. ; Seidman, David N ; Jones, N. G. / The effect of zirconium on the omega phase in Ti-24Nb-[0–8]Zr (at.%) alloys. In: Acta Materialia. 2018 ; Vol. 153. pp. 62-70.
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The effect of zirconium on the omega phase in Ti-24Nb-[0–8]Zr (at.%) alloys. / Pang, E. L.; Pickering, E. J.; Baik, S. I.; Seidman, David N; Jones, N. G.

In: Acta Materialia, Vol. 153, 01.07.2018, p. 62-70.

Research output: Contribution to journalArticle

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T1 - The effect of zirconium on the omega phase in Ti-24Nb-[0–8]Zr (at.%) alloys

AU - Pang, E. L.

AU - Pickering, E. J.

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AU - Seidman, David N

AU - Jones, N. G.

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AB - Ti-Nb based β-Ti alloys are a promising new class of superelastic, shape-memory, and low-modulus materials for a wide range of applications. A critical phase in β-Ti alloys is the ω phase, which greatly affects the mechanical properties and superelastic/shape-memory behaviour of these materials. Zirconium, an important alloying constituent in many β-Ti alloys, is generally regarded as an ω suppressant, but the body of evidence supporting this view is unconvincing and includes a number of conflicting reports. In this article, the role of Zr on ω phase formation in Ti-Nb alloys is clarified using X-ray diffraction, transmission electron microscopy, and atom-probe tomography. Zirconium additions were found to suppress the formation of athermal ω phase upon quenching from high temperature. However, up to 8 at.% Zr additions to a Ti-24 at.% Nb alloy had little effect on the formation of isothermal ω phase following aging at 300 °C after 100 h. Furthermore, the isothermal ω precipitates were found to be strongly depleted in Nb but only weakly depleted in Zr. These results challenge the belief that Zr suppresses isothermal ω formation in β-Ti alloys, a result that is likely to be applicable beyond the Ti-Nb system considered here and information that can be used to assist in the design of future β-Ti alloys.

KW - Atom-probe tomography

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