Discerning phase-matrices for individual nitride inclusions within ultra-high-strength steel: experiment driven DFT investigation

Abstract

Non-metallic inclusions play a decisive role in the steel's performance. Therefore, their determination and control over their formation are crucial to engineer ultra-high-strength steel. Currently, bare experimental approaches are limited in the identification of non-metallic inclusions within microstructural phases of complex steel matrices. Herein, we performed a density functional theory study on the characteristics of different nitride inclusions as observed in spectro-microscopy studies. As per the simulations, TiN inclusions preferentially formed in the austenite matrix, while the ferrite matrix generally hosts BN inclusions. Furthermore, although the presence of both BN and TiN inclusions in the Fe₃C matrix is possible, their formation is impeded because of the strong inclusion–carbon interactions. The observed regularity in the formation of nitride inclusions in different phases of steel was also confirmed by the comparison of simulated and experimental K-edge XAS spectrum of nitride inclusions. Our work shed the light on the formation of nitride inclusions in different steel matrices and facilitates their further experimental identification.