Mechanical and corrosion behaviour of a Ti-Al-Nb alloy after deformation at elevated temperatures

• Published in: Materials and corrosion Vol. 59; no. 12; pp. 919 - 928
• Main Authors: Popa, M. V., Raducanu, D., Vasilescu, E., Drob, P., Cojocaru, D., Vasilescu, C., Ivanescu, S., Rosca, J. C. Mirza
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.12.2008; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: Applied sciences; Corrosion; Corrosion environments; EIS; Exact sciences and technology; mechanical properties; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; microstructure; open circuit potential gradients; thermo-mechanical processing; Temperature; Aluminium base alloys; Deformation; Corrosion; Mechanical properties; Aluminium; High temperature
• ISSN: 0947-5117; 1521-4176
• DOI: 10.1002/maco.200805003

The mechanical properties of Ti6Al7Nb alloy deformed and heat treated at elevated temperatures were correlated with its microstructure and corrosion behaviour in Ringer (of different pH values: 2.49, 6.9 and 8.9) and Ringer–Brown solutions. Microstructural analysis revealed a Widmanstatten structure for the alloys deformed at 1100 °C (β field) and structure with α grains at 930 °C (α + β field). The thermo‐mechanical processing improved the electrochemical behaviour of Ti6Al7Nb alloys, especially their passive state. Open circuit potential variations in time reflected more compact, stable, resistant passive films on the surface of the treated alloys. Open circuit potential gradients simulating the non‐uniformities of pH along the implant surface have very low values that cannot generate galvanic corrosion. Corrosion rates and ion release are very much reduced. Impedance spectra were fitted with a two time‐constants equivalent circuit for some alloys and with three time‐constants equivalent circuit for other alloys.