Evaluation of Phase Equilibria Involving the Liquid Phase in the Hf-Si System

• Published in: Journal of phase equilibria and diffusion 2014-10, Vol.35 (5), p.622-630
• Main Authors: Gigolotti, J. C. J., Nunes, C. A., Suzuki, P. A., Coelho, G. C.
• Format: Article
• Language: English
• Subjects: Alloys; Ceramics; Composites; Crystallography and Scattering Methods; Diffraction; Engineering Thermodynamics; Glass; Hafnium; Heat and Mass Transfer; Invariants; Liquid phases; Metallic Materials; Natural Materials; Phase diagrams; Phase equilibria; Physics; Physics and Astronomy; Silicon; Thermodynamics
• ISSN: 1547-7037; 1863-7345; 1934-7243
• DOI: 10.1007/s11669-014-0330-x

Metal-silicon-boron (Me-Si-B) alloys have been extensively studied due to their potential to develop high temperature structural materials. In this sense, information from accurate phase diagram becomes important. This work presents results of detailed microstructural characterization of as-cast hafnium-silicon alloys to assess the liquid composition associated to the invariant reactions of this system. The alloys were prepared by arc melting from high purity hafnium and silicon under argon atmosphere. The phases present in the alloys were identified by scanning electron microscopy and x-ray diffraction. Important discrepancies were found between the data obtained in this work and those of the most recent phase diagrams, especially the composition of the liquid phase in the following reactions: L + Hf 5 Si 3 ⇄ Hf 2 Si, 32.5 at.% Si instead of 21 at.% Si, L + Hf 3 Si 2 ⇄ Hf 5 Si 3 , 37.0 at.% Si instead of 30.3 at.% Si and L + Hf 5 Si 4 ⇄ HfSi, 52.5 at.% Si instead of 58.3 at.% Si.