Influence of vibrational free energy on the phase stability of alloys from first principles
2015 (English)Manuscript (preprint) (Other academic)
We have developed a method to accurately and efficiently determine the vibrational free energy as a function of temperature and pressure for substitutional alloys from first principles. Taking the example of the technologically important hard coating alloy Ti1-xAlxN as an example, we investigate the effect on the vibrational free energy of substituting Ti for other group IV elements. By constructing the phase diagrams for these three alloys, we show why Zr1-xAlxN and Hf1-xAlxN are so difficult to experimentally synthesise in a metastable solid solution: both have solubility regions that span only a small low-AlN concentration range at temperatures above 1500 K. Moreover, Hf1-xAlxN is dynamically unstable at low temperatures and across most of the concentration range. We also show the chemical and thermal expansion effects dominate mass disorder in the Gibbs free energy of mixing.
Place, publisher, year, edition, pages
Condensed Matter Physics Physical Sciences
IdentifiersURN: urn:nbn:se:liu:diva-122958OAI: oai:DiVA.org:liu-122958DiVA: diva2:875201