Applying the Effective Bond Energy Formalism (EBEF) to Describe the Mu (μ) and Sigma (σ) Phases in the Co-Cr-Ni-W System

The Effective Bond Energy Formalism (EBEF) is used in the present work to describe the mu (mu) and sigma (6) phases in the Co-Cr-Ni-W system. This represents the first time that: i) mu is described using the EBEF, and ii) two Topologically Closed-Packed (TCP) phases are simultaneously described with the EBEF. Both phases are described with thermodynamic models that are more consistent with their real crystallography and their formation energies are determined using new Density Functional Theory (DFT) calculations. The good agreement obtained between the calculated phase diagrams and the experimental results indicates once again that the EBEF is suitable to describe complex TCP phases. Furthermore, the implementation of the EBEF led to a significant reduction in the number of adjustable/ternary parameters needed, when the present thermodynamic assessment is compared to descriptions available in the literature.