Abstract
In the realm of materials science within the hydrogen sector, understanding the interfacial energy between a hydride and its parent matrix is crucial for modeling metal-hydride phase transformations and their influence on hydrogenation kinetics. In this investigation, we employ atomistic models and micromechanical analysis to deconvolute the interconnected chemical and elastic components of the interphase boundary energy within the FeTi metal-hydride system. Our approach involves atomistic models of the interface between metal and hydride and the quantification of the chemical contribution to the interphase boundary energy by employing density functional theory (DFT) calculations together with appropriate thermodynamic equations. Additionally, we delve into the elastic contribution to the interphase boundary energy and ascertain the habit plane of ß-FeTiH formation. This determination is achieved by combining the quantification of the chemical contribution the elastic stiffness tensor of each phase within micromechanical analysis, both derived through rigorous DFT calculations. Our analysis unveil the progression in the development of the ß-FeTiH phase. Initially, it exhibits near-isotropic behavior that subsequently evolves towards growth along a specific direction tilted approximately 19° relative to the (001)ß plane of the ß-phase. Ultimately, it attains a habit plane parallel to the (001)ß plane. These findings offer valuable insights into the intricate interplay between chemical and elastic contributions to hydride formation. Such insights hold significant implications for the integration of micromechanics into phase field simulations of FeTi alloy hydrogenation—an ongoing focal point of research in our group.
