Historically, CALPHAD assessments considered many types of experimental data from various types of experiments to create an optimised thermodynamic description. As theoretical calculations become more readily available, new types of relevant data are accessible which give us new insights into materials that can be challenging or impossible to obtain experimentally.
Using first-principles calculations, we can obtain information about defect formation energies, never seen but related metastable phases, and stable phases that are kinetically prevented from forming. These insights on an electronic and atomic level can be used to explain the origins of short- and long-range atomic ordering and can provide a holistic understanding of order-disorder processes that is difficult to obtain experimentally. In some cases, this new data can be incorporated into the assessment directly as part of the conventional optimisation process, but in other cases new models must be developed to accurately describe the underlying physics. Using the ultra-high temperature ceramic zirconium carbide as an example, this talk shows how first-principles calculations can unveil the mechanisms of ordering throughout its wide non-stoichiometry from 0 K up to the maximum melting point of 3700 K, incorporating these insights into a CALPHAD description.
This webinar is part of our Expert User Series, which invites experts from industry and academia to present their work with Thermo-Calc products.