Microscopic study of gum-metal alloys: A role of trace oxygen for dislocation-free deformation

Naoyuki Nagasako*, Ryoji Asahi, Dieter Isheim, David N Seidman, Shigeru Kuramoto, Tadahiko Furuta

*Corresponding author for this work

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

A class of Ti-Nb-Ta-Zr-O alloys called gum metal are known to display high strength, low Young's modulus and high elastic deformability up to 2.5%, simultaneously, and considered to deform by a dislocation-free deformation mechanism. A trace of oxygen (∼1%) in gum metal is indispensable to realize such significant properties; however, the detailed mechanism and the role of the oxygen has not been understood. To investigate an effect of trace oxygen included in gum metal, first-principles calculations for gum-metal approximants including zirconium and oxygen are performed. Calculated results clearly indicate that oxygen site with less neighboring Nb atom is energetically favorable, and that Zr-O bonding has an important role to stabilize the bcc structure of gum metal. The three-dimensional atom-probe tomography (3-D APT) measurements for gum metal were also performed to identify compositional inhomogeneity attributed to the trace elements. From the 3-D APT measurements, Zr ions bonding with oxygen ions are observed, which indicates existence of Zr-O nano-clusters in gum metal. Consequently, it is found that (a) coexistence of Zr atom and oxygen atom improves elastical stability of gum metal, (b) inhomogeneous distribution of the compositions induced by the trace elements causes anisotropical change of shear moduli, and (c) Zr-O nano-clusters existing in gum metal are expected to be obstacles to suppress movemen of dislocations.

Original languageEnglish (US)
Pages (from-to)347-354
Number of pages8
JournalActa Materialia
Volume105
DOIs
StatePublished - Feb 15 2016

Keywords

  • Dislocation-free deformation mechanism
  • First-principles calculation
  • Three-dimensional atom-prove tomography
  • Ti alloys

ASJC Scopus subject areas

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

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