A critical thermodynamic assessment of the metastable c-TiAlZrN coatings,
which are reported to spinodally decompose into triple domains, i.e., c-TiN,
c-AlN, and c-ZrN, was performed via the CALculation of PHAse Diagram
(CALPHAD) technique based on the limited experimental data as well as the
first-principles computed free energies. The metastable c-TiAlZrN coatings
were modeled as a pseudo-ternary phase consisting of c-TiN, c-AlN and c-ZrN
species, and described using the substitutional solution model. The
thermodynamic descriptions for the three boundary binaries were directly
taken from either the CALPHAD assessment or the first-principles results
available in the literature except for a re-adjustment of the pseudo-binary
c-AlN/c-ZrN system based on the experimental phase equilibria in the
pseudo-ternary system. The good agreement between the calculated phase
equilibria and the experimental data over the wide temperature range was
obtained, validating the reliability of the presently obtained thermodynamic
descriptions for the c-TiAlZrN system. Based on the present thermodynamic
description, different phase diagrams and thermodynamic properties can be
easily predicted. It is anticipated that the present thermodynamic
description of the metastable c-TiAlZrN coatings can serve as the important
input for the later quantitative description of the microstructure evolution
during service life.
Thermodynamic description of the Al-Cu-Yb ternary system supported by first-principles calculations
