Reactivity of a Ti-46Al-8Nb Alloy in Air at 700 - 900 oC

Elżbieta M. Godlewska ,  Marzena M. Mitoraj 

AGH University of Science and Technology, Faculty of Materials Science and Ceramics (AGH UST), Mickiewicza 30, Kraków 30-059, Poland

Abstract

A titanium aluminide alloy, Ti-46Al-8Nb (at %), with a lamellar structure (γ+α2) was tested for oxidation resistance in air at 700, 800, 850, and 900 °C in isothermal and thermal cycling conditions (1-hour and 20-hour hot-dwell time). The oxidation behaviour was assessed by means of mass change measurements as a function of time. The X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used to determine phase composition and chemical composition of the oxidation products. Surfaces of the oxide scales were examined by optical microscopy (OM) and scanning electron microscopy (SEM). Cross-sections of the selected samples were analysed using both secondary electron images and backscattered electron images (SEI and BEI) as well as transmission electron microscopy (TEM).
In isothermal tests the mass gains increased with temperature, the oxidation kinetics followed approximately a parabolic rate law. The calculated parabolic rate constants ranged from about 10-12 to 10-10 kg2/m4s. The oxide scales were built of Al2O3 and TiO2, the former being the main component of the outermost layer. The innermost layer contained oxygen and all three elements of the alloy with varying local concentrations. The oxidation behaviour of Ti-46Al-8Nb was compared with a commercial titanium alloy, WT4 (Ti-6Al-1Mn), and with selected oxidation-resistant alloys.

Legal notice
  • Legal notice:

    Copyright (c) Pielaszek Research, all rights reserved.
    The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
    In every case, proper references including Author(s) name(s) and URL of this webpage: http://science24.com/paper/8013 must be provided.

 

Presentation: Poster at E-MRS Fall Meeting 2006, Symposium I, by Marzena M. Mitoraj
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-16 08:13
Revised:   2009-06-07 00:44
Google
 
Web science24.com
© 1998-2021 pielaszek research, all rights reserved Powered by the Conference Engine