Tendrá lugar el 3 de septiembre a las 11:00, en la sala de seminario.

Resumen

Hydrogen embrittlement in structural alloys is a microstructure-dependent phenomenon, governed by
the interplay of composition, grain boundaries, dislocation density, and interface architecture.
Microstructural heterogeneity, arising from variations in grain size, phase distribution, defect density, and
residual stresses, controls hydrogen transport, trapping, and deformation mechanisms at local length
scales. Due to hydrogen’s high mobility and atomic size, uncovering its role in mechanical degradation
requires probing hydrogen-microstructure interactions under well-controlled, in situ conditions.

We combine time-resolved nanoindentation, nanoscratching, and micropillar compression with
continuous electrochemical hydrogen charging in a custom-designed cell integrated into a commercial
nanoindenter [1]. This setup enables operando monitoring of hydrogen absorption, release, and
mechanical response, while tailored charging protocols allow separation of diffusible and trapped
hydrogen effects. Using binary Fe-X (X = Cr, Ni, Al) model alloys with independently tuned grain size and
dislocation density, engineered via thermomechanical processing to span coarse-grained (>600 μm) to
nanocrystalline (~200 nm) states, we systematically isolate the influence of individual microstructural
features [2,3].

Hydrogen consistently induces hardening by modifying dislocation nucleation, mobility, and interactions.
In coarse-grained, low-dislocation density alloys, these effects are largely reversible upon hydrogen
removal. In contrast, nanocrystalline materials and high-dislocation-density systems exhibit prolonged
hardening due to enhanced hydrogen trapping at grain boundaries and dislocations. Nanoscratching
reveals increased resistance to shear-driven plasticity near hydrogen-trapped interfaces, highlighting the
role of microstructural architecture in local deformation resistance.

Extending the study to commercial ferritic, pearlitic, and austenitic steels confirms that hydrogen
sensitivity is not a material constant but also a function of manufacturing history, such as rolling, heat
treatment, and cold working, that dictates hydrogen uptake, retention, and mechanical performance
under service conditions.