Observation of defects in deformed and hydrogen-charged iron by electron microscopy

Defect states in cold-worked iron specimens electrolytically hydrogen charged were characterized by a combination of optical microscopy, scanning electron microscopy, and high-resolution electron microscopy. For deformations of up to 20% and 13% (for cold-rolled and elongated specimens, respectively), the density of hydrogen-induced cracks and surface blisters decreased with the increases in the amount of deformation. Vacancy clusters with sizes of the order of 1 nm were observed in cold-rolled and hydrogen-charged iron specimens. The size and the density of the observed vacancy clusters were of the same order as those predicted previously based on positron-annihilation results. The results are explained by hydrogen trapping.