TY - JOUR
T1 - Microscopic study of gum-metal alloys
T2 - A role of trace oxygen for dislocation-free deformation
AU - Nagasako, Naoyuki
AU - Asahi, Ryoji
AU - Isheim, Dieter
AU - Seidman, David N.
AU - Kuramoto, Shigeru
AU - Furuta, Tadahiko
N1 - Publisher Copyright:
© 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
PY - 2016/2/15
Y1 - 2016/2/15
N2 - 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.
AB - 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.
KW - Dislocation-free deformation mechanism
KW - First-principles calculation
KW - Three-dimensional atom-prove tomography
KW - Ti alloys
UR - http://www.scopus.com/inward/record.url?scp=84953708726&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84953708726&partnerID=8YFLogxK
U2 - 10.1016/j.actamat.2015.12.011
DO - 10.1016/j.actamat.2015.12.011
M3 - Article
AN - SCOPUS:84953708726
VL - 105
SP - 347
EP - 354
JO - Acta Materialia
JF - Acta Materialia
SN - 1359-6454
ER -