CALPHAD, preparation, and mechanical properties of quaternary solid solution nitrides with various nitrogen stoichiometry

Abstract

High-entropy ceramics have gained increasing interest due to unique properties unattainable by traditional materials. Though a large number of high-entropy ceramics have emerged, there was still in lack of theoretical predictions of phase composition on multicomponent solid solutions, which was probably caused by the composition complexity. In this work, employing Thermo-Calc and TCHEA4 database, a series of equilibrium phase data was generated from quaternary solid solution nitrides formed by the five elements of Ti, V, Cr, Zr, and N, while five quaternary solid solution nitrides with various nitrogen stoichiometry were prepared by SPS utilizing commercially available transition metal and their nitrides at 1600 °C. The detection of phase composition during the experiment and thermodynamic calculation confirmed that an increase in nitrogen content was beneficial for the formation of a single-phase solid solution. Due to the variation of nitrogen stoichiometry, the concentrations of nitrogen-metal bonds changed accordingly, resulting in different relative densities and mechanical properties. On the basis of the experimental data, CALPHAD, with a maximum absolute error of only 8.31 %, was established, providing a powerful tool for predicting phase in the complex composition-temperature space of compositionally complex ceramics.