Alloying element Ag modifies the behavior of H and defects in Pd alloys

Although alloying can significantly increase the hydrogen permeability of palladium (Pd) and solve the problem of hydrogen embrittlement in service, the intrinsic mechanism has not been revealed. Here, we report intuitive differences in the nucleation, growth and distribution of dislocation loops in Pd and PdAg alloys by in-situ hydrogen irradiation in TEM. The results reveal that alloying element Ag not only modifies the behavior of H, but also induces defects to change from the original long-range one-dimensional (1D) diffusion to short-range three-dimensional (3D) diffusion, which significantly delays the aggregation and growth of dislocation loops and reduces the total irradiation damage and H retention. A new strategy to improve hydrogen embrittlement resistance is proposed, i.e., constructing dense dislocation loop bands (or other sinks that can efficiently trap H) in front of grain boundaries to prevent H from diffusing into the grain boundaries.