Establishing the Role of Hydrogen in Metal Plasticity

Hydrogen (H) is essential to decarbonize industry, but its use today is limited because it embrittles the metals and alloys required to store/distribute it. Despite 150 years of research, the fundamental mechanisms of H-embrittlement are still poorly understood. H atoms form a solid solution of interstitials in structural metals that affect the behavior of dislocations. While dislocations are essential to understand plasticity and deformations, it is still unclear whether H enhances or reduces their mobility. This matter is hotly debated, as no technique can measure dislocations and their motion deep inside bulk crystals during stress. We developed time-resolved and 3D dark-field X-ray microscopy (DFXM) and use it to study the interactions of deep subsurface dislocations. We now seek to use DFXM to directly measure how H alters the structure and interactions forces between dislocations, offering the first direct measurements to reconcile conflicting H-altered mobility models.