Experimental determination and thermodynamic assessment of phase equilibria in the como system

K. Oikawa, U. R. Kattner, J. Sato, T. Omori, M. Jiang, K. Anzai, K. Ishida

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Phase equilibria of the solid phases including the magnetic and martensitic transformation temperatures in the CoMo system were investigated using two-phase alloys, the diffusion couple technique, differential scanning calorimetry, and vibrating sample magnetometry. Furthermore, ab initio calculations of D0 19-Co 3Mo and several fcc-base ordered structures, including metastable compounds, were carried out to estimate the formation energy. Based on these results, a thermodynamic assessment using the CALPHAD method was performed. A foursublattice model was used for the fcc-base phase to describe the orderdisorder phase transformation. For the μ phase, both a three and a foursublattice model were applied. The set of thermodynamic values describing the Gibbs energy of the CoMo system reproduces the experimental phase diagram well. The four-sublattice model for the μ phase reproduces the site fractions as well as the phase boundaries better than the threesublattice model. The calculated metastable fcc-base phase diagram considering chemical and magnetic ordering is also reasonable. This is important for estimating the phase stability of the L1 2 phase in Co-base γ/γ' superalloys.

Original languageEnglish
Pages (from-to)1425-1435
Number of pages11
JournalMaterials Transactions
Volume53
Issue number8
DOIs
Publication statusPublished - 2012

Keywords

  • First-principles
  • Orderdisorder transition
  • Phase diagram
  • Superalloys
  • Thermodynamic

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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