Influence of Si and C additions on microstructure and mechanical properties of the Ti-43.5Al-1Mo-4Nb-0.1B alloy

• Published in: Materials at high temperatures Vol. 33; no. 4-5; pp. 542 - 548
• Main Authors: Denquin, Anne, Huvelin, Zhao, Signori, Loris, Bachelier-Locq, Agnès, Perrut, Mikael, Naka, Shigehisa
• Format: Journal Article
• Language: English
• Published: Taylor & Francis 28.06.2016
• Subjects: creep; heat treatment; Intermetallics; mechanical properties; microstructure; phase transformation
• ISSN: 0960-3409; 1878-6413
• DOI: 10.1080/09603409.2016.1177303

Separate effects of 0.3 at% Si and 0.2 at% C additions have been investigated on the Ti-43.5Al-1Mo-4Nb-0.1B alloy. Both elements appear to stabilise the γ phase. Si addition induces an increase in both γ-lamellar and γ-grain volume fractions. A heterogeneous distribution of primary and secondary silicides is observed in Al-rich regions of the microstructure, but silicon appears to be mainly in solid solution in the lamellar structure. The solid solution effect of silicon in the more plastically deformable β phase is probably very limited because of the high volume fraction of α 2 in this alloy. This may explain the lack of beneficial effect of 0.3 at% of silicon on both tensile and creep properties. Carbon appears to stabilise the γ phase through an increase in γ-grain volume fraction and is found to be in solid solution in the lamellar structure. Our results suggest a very strong solid solution effect of carbon, since addition as low as 0.16 at% leads to an increase in yield strength at room and high temperature, a reduction in the secondary creep rate and a longer creep life.