Phase transformations and mechanical properties of biocompatible Ti–16.1Nb processed by severe plastic deformation

Ajit Panigrahi, Matthias Bönisch, Thomas Waitz, Erhard Schafler, Mariana Calin, Jürgen Eckert, Werner Skrotzki, Michael Zehetbauer

A coarse grained biocompatible Ti–16.1Nb (wt.%) alloy was used to study

the impact of severe plastic deformation on microstructural changes,

phase transformations, and mechanical properties. The starting material,

showing a rather low value of Young’s modulus (66 GPa), contained

orthorhombic α″ martensite. Hydrostatic pressure of 4 GPa solely yields a partial transformation to the ω-phase; increasing the pressure to 8 GPa increases the volume fraction of the ω-phase

and causes a concomitant increase of Young’s modulus. By processing

samples through high pressure torsion at room temperature, i.e. applying

both hydrostatic pressure and shear deformation, a nanocrystalline

structure was obtained. The samples almost exclusively contained the ω-phase and showed rather high values of Young’s modulus (up to 130 GPa) and hardness (up to 4.0 GPa). The ω-phase

formed during high pressure torsion revealed stability upon unloading.

However, upon heating to about 500 °C the ω-phase decomposes into a

phase mixture of hexagonal α and body centred cubic β phases which is still ultra-fine. Cold rolling and folding achieves a microstructure consisting of ω, α/α′ and α

phases. Concomitant decrease of grain size and increase of defect

density yield a hardness (3.3 GPa) which is smaller than that of high

pressure torsion but a Young’s modulus of about 100 GPa being closer to

that of the initial material.

Physics of Nanostructured Materials
External organisation(s)
Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Technische Universität Dresden
Journal of Alloys and Compounds
No. of pages
Publication date
Peer reviewed
Austrian Fields of Science 2012
103018 Materials physics, 210004 Nanomaterials
ASJC Scopus subject areas
Mechanics of Materials, Mechanical Engineering, Metals and Alloys, Materials Chemistry
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