Segregation of solute atoms in ZrC grain boundaries and their effects on grain boundary strengths

• Published in: Journal of materials science & technology 2022-02, Vol.101, p.234-241
• Main Authors: Dai, Fu-Zhi, Sun, Yinjie, Ren, Yixiao, Xiang, Huimin, Zhou, Yanchun
• Format: Article
• Language: English
• Subjects: First-principles calculation; Grain boundary; Machine learning; Segregation; Strength; ZrC
• ISSN: 1005-0302; 1941-1162
• DOI: 10.1016/j.jmst.2021.05.058

•Segregation of solid solutes in ZrC grain boundaries are studied by first-principles.•The segregation is dominated by atomic size effect.•Segregation energy can be predicted by machine learning method.•ZrC grain boundaries can be strengthened by segregation of smaller atoms.•Strengthening grain boundaries can improve high temperature strengths of ZrC. ZrC is a promising candidate for the application in ultra-high temperature regime due to its unique combination of excellent properties, such as high melting point, good chemical inertness and high temperature stability. The rapid decrease of strength at high temperatures, however, is one of the obstacles that impedes its practical services. Strengthening of grain boundaries by solute segregation is believed to be an effective way to improve its high temperature performance. Therefore, the segregation tendency of ten solid solute atoms, including Sc, Ti, V, Cr, Y, Nb, Mo, Hf, Ta, W, in ZrC grain boundaries, and the strengthening/weakening effects on grain boundaries due to segregation are investigated by first-principles calculations. The segregation tendency is found dominated by the size effect, which is confirmed by both a qualitative analysis and a quantitative approach based on support vector regression. It means that big atoms tend to segregate to grain boundary sites with local expansions, while small atoms tend to segregate to grain boundary sites with local compressions. Simulations on stress-strain responses indicate that segregation of small atoms (Ti, V, Cr, Nb, Ta, Mo, W) can usually improve grain boundary strengths by inducing compression strains to grain boundaries, even though there is also an exception. In contrast, segregation of Sc and Y will soften grain boundaries. The results reveal that strengthening of grain boundaries by solute segregation is a valuable avenue to enhance high temperature mechanical properties of ZrC, providing guidelines for further design of ZrC based materials. [Display omitted]