  When H, the lightest, smallest and most abundant atom in the universe, makes
its way into a high-strength alloy (>650 MPa), the material's load-bearing
capacity is abruptly lost. This phenomenon, known as H embrittlement, was
responsible for the catastrophic and unpredictable failure of large engineering
structures in service. The inherent antagonism between high strength
requirements and H embrittlement susceptibility strongly hinders the design of
lightweight yet reliable structural components needed for carbon-free
hydrogen-propelled industries and reduced-emission transportation solutions.
Inexpensive and scalable alloying and microstructural solutions that enable
both, an intrinsically high resilience to H and high mechanical performance,
must be found. Here we introduce a counterintuitive strategy to exploit
typically undesired chemical heterogeneity within the material's microstructure
that allows the local enhancement of crack resistance and local H trapping,
thereby enhancing the resistance against H embrittlement. We deploy this
approach to a lightweight, high-strength steel and produce a high-number
density Mn-rich zones dispersed within the microstructure. These solute-rich
buffer regions allow for local micro-tuning of the phase stability, arresting
H-induced microcracks thus interrupting the H-assisted damage evolution chain,
regardless of how and when H is introduced and also regardless of the
underlying embrittling mechanisms. A superior H embrittlement resistance,
increased by a factor of two compared to a reference material with a
homogeneous solute distribution within each microstructure constituent, is
achieved at no expense of the material's strength and ductility.
