The Ta-Si System: Reevaluation of the Liquid Compositions in the Invariant Reactions and Determination of the Invariant Reaction Involving Both [beta]Ta^sub 5^Si^sub 3^ and [alpha]Ta^sub 5^Si^sub 3^ Phases

• Published in: Journal of phase equilibria and diffusion 2015-06, Vol.36 (3), p.209
• Main Authors: Da Silva, Antonio Augusto, Araújo, Pinto, Ramos, Erika Coaglia, Trindade, Faria, Maria Ismênia, Sodero, Toledo, Coelho, Gilberto Carvalho, Nunes, Carlos Angelo
• Format: Article
• Language: English
• ISSN: 1547-7037; 1934-7243
• DOI: 10.1007/s11669-015-0374-6

Transition metal silicides are of great interest as high-temperature structural materials. Recent investigations aimed at the development of high-temperature Niobium-base structural alloys where silicide phases play a major role. Tantalum, in spite of its high atomic mass, is a potential micro-alloying element in these alloys to provide higher strength at high temperatures. In this work the invariant reactions of the Ta-Si system were reviewed via microstructural characterization of as-cast alloys. Samples were prepared by arc melting and their microstructures were characterized by scanning electron microscopy and x-ray diffractometry. The results confirmed the solid phases and the nature of the invariant reactions in this system. Few corrections in the currently accepted phase diagram are suggested: (1) the composition of the liquid phase that participates in peritectic formation of Ta^sub 2^Si should be near 32 at.% Si instead of 28 at.% Si; (2) the inclusion of the [beta]Ta^sub 5^Si^sub 3^ [alpha]Ta^sub 5^Si^sub 3^ + L metatectic reaction involving the [beta]Ta^sub 5^Si^sub 3^, [alpha]Ta^sub 5^Si^sub 3^ and L phases.