Effective Bond Energy Formalism Description of the μ Phase in the Co-Cr-Ni-W System
The thermodynamic database is developed for the Co-Al-Cr-Ni-Re-Ru-Ta-Ti-V-W system using the regular solution type model for the disordered solution phase and the compound energy formalism for the ordered phases. The model parameters are assessed using data from experiments and theoretical predictions, such as density functional theory (DFT). It was found that the prediction of the topologically close-packed (TCP) phases with the initial version of the database was not reliable because the descriptions were based on the formation energies of the binary endmembers of these phases. The reliability can be improved by adding parameters for the formation energy of the ternary endmembers. However, this is not feasible for a large database because the generation of ternary endmember data using DFT would be an enormous computational effort.
The effective bond energy formalism (EBEF) has shown great promise to produce realistic predictions of higher component system just by using parameters for the binary system. Therefore, the EBEF is being explored for the complex intermediate phases within the framework of existing descriptions of the binary and ternary subsystems to improve reliability of predictions of higher-component systems. Initial work] on the σ phase in the Co-Cr-Ni-Re system has shown that the EBEF description of this phase gave more reliable predictions of its stability range compared to traditional compound energy formalism (CEF) descriptions. Furthermore, the implementation of the EBEF led to a significant reduction in the number of adjustable/ternary parameters needed compared to CEF descriptions available in the literature. The present work expands the use of the EBEF to the μ phase in the Co-Cr-Ni-W system in addition to the previously described σ phase.
See more of: PSDK XV: Phase Stability and Diffusion Kinetics