Liquid-solid phase equilibria in metal-rich Nb-Ti-Hf-Si alloys

Y. Yang, B. P. Bewlay, Y. A. Chang

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

A thermodynamic description of the Nb-Ti-Hf-Si system is extrapolated from descriptions of the constituent Nb-Ti-Si, Nb-Hf-Si, Hf-Ti-Si, and Nb-Hf-Ti systems using the CALPHAD technique. From this thermodynamic description, the liquidus projection at the metal-rich region of the Nb-Ti-Hf-Si system with the Si concentration up to 40% is calculated. The calculated liquidus surface at this region consists of six primary solidification regions: (Nb), Hf 2Si, (Hf,Ti) 5Si 3, (Nb,Ti) 3Si, αNb 5Si 3, and βNb 5Si 3. Three five-phase equilibria involving these phases are identified on the liquidus surface by this calculation. They are L + (Nb) + αNb 5Si 3 → Hf 2Si + (Nb,Ti) 3Si at 1814°C, L + Hf 2Si + α Nb 5Si 3 → (Hf, Ti) 5Si 3 + (Nb, Ti) 3 Si at 1739°C, L + Hf 2Si → (Nb) + (Hf, Ti) 5Si 3 + (Nb, Ti) 3Si at 1400°C. To validate the calculated liquidus surface, a total of 10 alloys was directionally solidified. The microstructure of these 10 as-cast alloys was examined by using scanning electron microscopy (back scatter electron (BSE) imaging) and energy dispersive spectrometry (EDS). The solidification simulation of these 10 alloys was then performed by using the Scheil model that is integrated in the multicomponent phase diagram calculation software Pandat. The observed phases presented in the as-cast microstructure of these 10 alloys are in good agreement with those predicted from the Scheil simulation.

Original languageEnglish
Pages (from-to)107-114
Number of pages8
JournalJournal of Phase Equilibria and Diffusion
Volume28
Issue number1
DOIs
StatePublished - Feb 2007
Externally publishedYes

Funding

This article was presented at the Multi-Component Alloy Thermodynamics Symposium sponsored by The Alloy Phase Committee of the joint EMPMD/SMD of the Minerals, Metals, and Materials Society (TMS), held in San Antonio, Texas, March 12-16, 2006, to honor the 2006 William Hume-Rothery Award recipient, Professor W. Alan Oates of the University of Salford, UK. The symposium was organized by Y. Austin Chang of the University of Wisconsin, Madison, WI, Patrice Turchi of the Lawrence Livermore National Laboratory, Livermore, CA, and Rainer Schmid-Fetzer of the Technische Universitat Clausthal, Clauthal-Zellerfeld, Germany.

Keywords

  • CALPHAD
  • Liquidus surface
  • Multicomponent
  • Phase diagram
  • Phase equilibria
  • Quaternary

Fingerprint

Dive into the research topics of 'Liquid-solid phase equilibria in metal-rich Nb-Ti-Hf-Si alloys'. Together they form a unique fingerprint.

Cite this