Oxidation and alpha-case formation in Ti–6Al–2Sn–4Zr–2Mo alloy

Journal Article · Thu Jan 15 00:00:00 EST 2015 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2014.11.023· OSTI ID:22476015

Gaddam, Raghuveer ^[1]; Sefer, Birhan ^[1]; Pederson, Robert ^[1]; Antti, Marta-Lena ^[1]

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1. Division of Materials Science, Luleå University of Technology, S-97187 Luleå (Sweden)

Isothermal heat treatments in ambient air were performed on wrought Ti–6Al–2Sn–4Zr–2Mo (Ti-6242) material at 500, 593 and 700°C for times up to 500 h. In the presence of oxygen at elevated temperatures simultaneous reactions occurred in Ti-6242 alloy, which resulted in the formation of an oxide scale and a layer with higher oxygen concentration (termed as alpha-case). Total weight gain analysis showed that there was a transition in the oxidation kinetics. At 500°C, the oxidation kinetics obeyed a cubic relationship up to 200 h and thereafter changed to parabolic at prolonged exposure times. At 593°C, it followed a parabolic relationship. After heat treatment at 700°C, the oxidation obeyed a parabolic relationship up to 200 h and thereafter changed to linear at prolonged exposure times. The observed transition is believed to be due to the differences observed in the oxide scale. The activation energy for parabolic oxidation was estimated to be 157 kJ/mol. In addition, alpha-case layer was evaluated using optical microscope, electron probe micro-analyser and microhardness tester. The thickness of the alpha-case layer was found to be a function of temperature and time, increasing proportionally, and following a parabolic relationship. The activation energy for the formation of alpha-case layer was estimated to be 153 kJ/mol. - Highlights: • Transition in oxidation kinetics was observed in Ti–6Al–2Sn–4Zr–2Mo alloy in the temperature range 500–700°C. • The activation energy for parabolic oxidation and for alpha-case formation is about 157 kJ/mol and 153 kJ/mol. • Thickness of alpha-case layer estimated by optical microscopy and electron probe microanalysis is comparable.

• OSTI ID: 22476015
• Journal Information: Materials Characterization, Vol. 99; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ACTIVATION ENERGY
ALLOY SYSTEMS
ALUMINIUM COMPOUNDS
DIFFUSION
ELECTRON MICROPROBE ANALYSIS
ELECTRON PROBES
HEAT TREATMENTS
LAYERS
METALLOGRAPHY
MOLYBDENUM COMPOUNDS
OPTICAL MICROSCOPY
OXIDES
SCANNING ELECTRON MICROSCOPY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0400-1000 K
THICKNESS
TIN COMPOUNDS
TITANIUM COMPOUNDS
ZIRCONIUM COMPOUNDS