In situ study of microstructural evolution in molybdenum during irradiation with low energy hydrogen ions

For the purpose of fundamental investigations of the response of materials exposed to a plasma, a duoplasma ion gun-transmission electron microscope (TEM) interface was constructed. This facility is capable of irradiating hydrogen ions with energies ranging from 0.1 to 10 keV onto TEM specimens, allowing in situ microstructural observations. The evolution of dislocations, bubbles and other aggregates in Mo at 573 K and their dependence on ion energy were investigated. The microstructures are found to be sensitive to ion energy. They are composed of a dislocation network and bubbles in the case of high energy ions, and in contrast to this, of a low density of planar dark images, which are expected to be platelet hydrogen clusters, in the case of low energy ions. It is suggested that the hydrogen retention, as well as materials damage, should significantly be reduced when the energy of hydrogen ions is reduced to or below the threshold of displacement damage production. (orig.)