Abstract
Understanding the interfacial properties and elastic behavior between a hydride phase and its parent matrix phase is essential for modeling metal-hydride phase transformations and their impact on hydrogenation kinetics. In this study, we investigate the interfacial properties of the ß-FeTiH hydride phase and its parent B2-FeTi matrix using atomistic models and first-principles calculations.
By employing interface models that consider the most favorable geometric orientation relationship, we quantify the interfacial energy and demonstrate the ability of this approach to decouple the chemical contribution from the intrinsic elastic energy originating from lattice parameter mismatches between the ß-FeTiH hydride and the B2-FeTi matrix.
Additionally, we analyze the elastic contribution to the orientation relationship and determine the habit plane of ß-FeTiH formation by convolving the stress-free transformation strain with the elastic properties of each phase, also obtained through first-principles methods.
Our results indicate an initial near isotropic behavior in the development of the ß-FeTiH phase, gradually progressing towards growth along a preferential direction tilted approximately 19° relative to the (001)ß plane of the ß-phase. This directional preference minimizes the total interfacial energy associated with the phase transition.
The findings of this study provide insights into the interplay between chemical and elastic contributions to the interfacial properties during the phase transformation of the ß-FeTiH hydride phase in the B2-FeTi matrix. Furthermore, these findings have significant implications for integrating micro-mechanics into phase field simulations of FeTi alloy hydrogenation, which is an ongoing research focus in our group.
