An updated thermodynamic description of the W-Co and W-Co-Cr systems with focus on ground state intermetallic phases

摘要

In this work, the thermodynamic description of the W-Co and the W-Co-Cr systems is updated with respect to the intermetallic phases. The ground state in the W-Co system is determined using density functional theory calculations and the results are parameterized in Calphad terms. The resulting thermodynamic description no longer results in a reappearing mu-phase region at lower temperatures, while maintaining a good fit to experimental data at high temperatures. In addition, the ground state calculations show that the currently accepted thermodynamic model for the p-phase will actually exclude the most stable compound configurations. Grouping of sites into sublattices, based on coordination number, has been a pragmatic (but necessary) means to reduce the number of parameters to be determined. An alternative approach is presented in this work, where simplification of a thermodynamic model is made based on energetics of the mu-phase.