Microstructure‐dependent hydrogen response via micromechanical testing under controlled hydrogen supply

Abstract

Hydrogen strongly influences the mechanical behavior of structural alloys, but its effects depend on microstructure. Grain size, orientation, dislocation density, and interfaces create heterogeneous pathways for hydrogen diffusion and trapping, producing highly local and time‐dependent mechanical
responses.
We combine nanoindentation, nanoscratching, and micropillar compression with active electrochemical hydrogen charging [1] to probe hydrogen‐induced changes in strength and plasticity at the scale of individual microstructural features in Fe‐Cr alloys. Controlled thermomechanical processing produced microstructures from coarse‐grained to nanocrystalline, with systematically varied dislocation density, enabling comparison of grain‐boundary‐ versus dislocation‐dominated regimes [2,3].
Hydrogen consistently causes hardening at the scale of individual microstructural features by pinning dislocations and modifying their nucleation and flow. In coarse‐grained alloys with low dislocation density, these effects are largely reversible after hydrogen removal. In contrast, alloys with higher
dislocation densities or increased grain‐boundary area exhibit persistent hardening, reflecting enhanced hydrogen trapping at dislocations and interfaces. Grain boundaries play a dominant role in governing hydrogen retention and mechanical response, while nanoscratching experiments reveal increased resistance to shear‐driven plasticity near hydrogen‐trapped interfaces.
These results demonstrate that hydrogen susceptibility is not an intrinsic bulk property, but instead emerges from the interplay between composition, microstructural architecture, and processing history. By connecting hydrogen transport and trapping phenomena to local mechanical performance, this work provides a framework for understanding and predicting hydrogen effects in structural alloys. Such insights are critical for the design of hydrogen‐resilient materials in energy and structural applications.

References
[1] M.J. Duarte, et al.; Journal of Materials Science, 2021, 56, 8732‐8744.
[2] J. Rao, et al.; International Journal of Hydrogen Energy, 2025, 102, 1103‐1115.
[3] J. Rao, et al.; Materials & Design, 2023, 232, 112143.