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High temperature oxidation resistance in titanium-niobium alloys

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Original languageEnglish
Pages (from-to)100-105
Number of pages6
JournalJournal of alloys and compounds
Volume643
DOIs
Publication statusPublished - 15 Sep 2015

Abstract

Titanium alloys are ideally suited for use as lightweight structural materials, but their use at high temperature is severely restricted by oxidation. Niobium is known to confer oxidation-resistance, and here we disprove the normal explanation, that Nb<sup>5+</sup> ions trap oxygen vacancies. Using density functional theory calculation, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) we show that Nb is insoluble in TiO<inf>2</inf>. In fact, the Ti-Nb surface has three-layer structure: the oxide itself, an additional Nb-depleted zone below the oxide and a deeper sublayer of enhanced Nb. Microfocussed X-ray diffraction also demonstrates recrystallization in the Nb-depleted zone. We interpret this using a dynamical model: slow Nb-diffusion leads to the build up of a Nb-rich sublayer, which in turn blocks oxygen diffusion. Nb effects contrast with vanadium, where faster diffusion prevents the build up of equivalent structures.

    Research areas

  • Computer simulations, Gas-solid reactions, Oxidation, Scanning electron microscopy SEM, Synchrotron radiation, Transition metal alloys and compounds

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