Abstract
Understanding the multiscale factors that play a role in the interphase boundary properties between hydride and its parent matrix is crucial for simulating the hydrogenation process. It influences the hydride’s stability, its rate of precipitation, and its morphology, thereby affecting the kinetics of the metal hydride transformation. In this study, atomic models and micromechanical analysis were employed to deconvolute the
naturally interconnected chemical and mechanical components of the interphase energy within the FeTi metal hydride system, showing its application within a quantitative phase field model
that is under development. In the first step, the approach involves the creation of atomistic models of the interfaces between metal and hydride together with the application of thermodynamics to quantify the chemical contribution to the interphase energy. In the second step, theoretical calculations of the elastic stiffness tensor of each phase are com
bined with the resulting chemical contribution to ascertain the strain energy and the habit plane of ß FeTiH formation through micromechanical analysis. Our research reveals the evolving ß FeTiH phase morphology. Initially, the hydride is nearly isotropic, gradually transitioning to growth at about 19° relative to the (001)ß plane of the ß phase. Ultimately, elastic energy dominance leads to interphase boundary coherency loss, with the hy
dride assuming a habit plane parallel to (001)ß, aligning well with literature micrographs. This approach offers valuable insights into the intricate interplay between chemical and elastic
contributions to hydride formation which can be generalized to any interstitial metal hydride. Moreover, it holds significant implications for the integration of micromechanics into phase field simulations of FeTi alloy hydrogenation — an ongoing research focus in our group.
