Effect of hydrogen on generation of lattice defects in shock-loaded Pd

The effect of hydrogen absorbed in fcc Pd lattice on the generation of dislocations and vacancies during plastic deformation by shock-loading was investigated in this work. Well annealed bulk Pd samples were firstly charged with hydrogen up to various hydrogen concentrations. Subsequently the samples were shock-loaded on a Split-Hopkinson apparatus. Shock-loading yields extremely high strain rate and causes intensive plastic deformation of the samples. Lattice defects of the shock-loaded samples were characterized by positron lifetime spectroscopy combined with X-ray diffraction. It was found that shock-loaded Pd samples exhibit not only high density of dislocations but also small vacancy clusters created by agglomeration of deformation-induced vacancies. Pre-charging of Pd samples with hydrogen increases both the dislocation density and the concentration of vacancy clusters.