Direct consideration of vacancies in CALPHAD modelling of zirconium carbide

Theresa Davey1, Ying Chen1

1. School of Engineering, Tohoku University, Japan

TMS 2020, San Diego, CA, USA

Contributed oral presentation in Algorithm Development in Materials Science and Engineering - Models and Algorithms for Microscale

Zirconium carbide is of interest in nuclear and aerospace industries due to its extremely high melting point. Its properties are strongly affected by significant structural vacancies. Conventional CALPHAD-type phase diagram models do not directly consider such defects, and the widely-used C-Zr phase diagram [1] has been shown to be intrinsically incompatible with our physical understanding of structural point defects [2].

In this work, state-of-the-art first-principles calculations of defect-related properties [3,4] are used to inform development of specific Gibbs energy models for cases where many structural point defects are present. Incorporating such information directly into the thermodynamic database produces a more physically consistent description and may allow further predictive ability.

[1] A Fernández Guillermet. Journal of Alloys and Compounds, 217:69–89, 1995.
[2] T Davey. PhD thesis (Imperial College London), 2017.
[3] AI Duff, et al.; Physical Review B, 91(21):214311, 2015.
[4] TA Mellan, et al., Physical Review B, 98(17):174116, 2018.