Thermal stability and phase transformations of martensitic Ti-Nb alloys

Author(s)

Matthias Bönisch, Mariana Calin, Thomas Waitz, Ajit Panigrahi, Michael Zehetbauer, Annett Gebert, Werner Skrotzki, Juergen Eckert

Abstract

Aiming at understanding the governing microstructural phenomena during

heat treatments of Ni-free Ti-based shape memory materials for

biomedical applications, a series of Ti–Nb alloys with Nb concentrations

up to 29 wt% was produced by cold-crucible casting, followed by

homogenization treatment and water quenching. Despite the large amount

of literature available concerning the thermal stability and ageing

behavior of Ti–Nb alloys, only few studies were performed dealing with

the isochronal transformation behavior of initially martensitic Ti–Nb

alloys. In this work, the formation of martensites (α' and α'')

and their stability under different thermal processing conditions were

investigated by a combination of x-ray diffraction, differential

scanning calorimetry, dilatometry and electron microscopy. The effect of

Nb additions on the structural competition in correlation with stable

and metastable phase diagrams was also studied. Alloys with 24 wt% Nb or

less undergo a transformation sequence on heating from room temperature to 1155 K. In alloys containing >24 wt% Nb α'' martensitically reverts back to β₀, which is highly unstable against chemical demixing by formation of isothermal ω_iso. During slow cooling from the single phase β domain α precipitates and only very limited amounts of α'' martensite form.

Organisation(s)

Physics of Nanostructured Materials

External organisation(s)

Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Technische Universität Dresden

Journal

Science and Technology of Advanced Materials

Volume

No. of pages

ISSN

1468-6996

DOI

https://doi.org/10.1088/1468-6996/14/5/055004

Publication date

10-2013

Peer reviewed

Yes

Austrian Fields of Science 2012

103009 Solid state physics, 103018 Materials physics

Keywords

Portal url

https://ucrisportal.univie.ac.at/en/publications/thermal-stability-and-phase-transformations-of-martensitic-tinb-alloys(f34b7b1e-9213-44c4-a50b-cf338d97547a).html