The Ta-Si System: Reevaluation of the Liquid Compositions in the Invariant Reactions and Determination of the Invariant Reaction Involving Both βTa5Si3 and αTa5Si3 Phases

• Published in: Journal of phase equilibria and diffusion Vol. 36; no. 3; pp. 209 - 217
• Main Authors: da Silva, Antonio Augusto Araújo Pinto, Ramos, Erika Coaglia Trindade, Faria, Maria Ismênia Sodero Toledo, Coelho, Gilberto Carvalho, Nunes, Carlos Angelo
• Format: Journal Article
• Language: English
• Published: New York Springer US 01-06-2015
• Subjects: Ceramics; Composites; Crystallography and Scattering Methods; Engineering Thermodynamics; Glass; Heat and Mass Transfer; Metallic Materials; Natural Materials; Physics; Physics and Astronomy; Thermodynamics; intermetallics; phase diagram; X-ray analysis; microstructure; phase transformation
• ISSN: 1547-7037; 1863-7345
• 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
2
Si should be near 32 at.% Si instead of 28 at.% Si; (2) the inclusion of the βTa
5
Si
3
 ↔ αTa
5
Si
3
 + L metatectic reaction involving the βTa
5
Si
3
, αTa
5
Si
3
and L phases.