LAUSR

Abstract Zirconium diboride (ZrB 2 ) is arguably one of the most important ceramic materials for applications involving extreme high temperatures and oxidizing environments such as those encountered in re-entry vehicles and hypersonic aircraft, among others. Accordingly, enhancing the creep resistance of ZrB 2 is of critical importance. A viable approach to achieve the latter is through the addition of substitutional atoms such as tungsten. In this work, using a combination of quantum mechanics based first-principles simulations and thermodynamic modeling; we present the essential elements of the W-ZrB 2 phase diagram to enable the design of enhanced creep-resistant ultra-high temperature ZrB 2 -alloys. In the course of the assessment, we estimate the Gibbs free energy of WB 2 , nonexistent in the literature to date, and based on the developed phase diagram, conclude that the solubility of tungsten in ZrB 2 does not occur below ∼1380 °C and that temperatures above ∼1700 °C are needed to dissolve 1 mol% of W in ZrB 2 .