Recent Studies of Hydrogen-related Defects in Iron-based Materials

The interactions between hydrogen, dislocations and vacancies that lead to the hydrogen embrittlement of iron-based materials have remained largely unknown with major impediments for the development of the infrastructure for hydrogen transport and storage. Recent studies of the hydrogen-induced lattice defects formed in pure iron and common austenitic stainless steels by positron annihilation lifetime spectroscopy have provided a breakthrough in understanding the controlling factors of the hydrogen embrittlement process. In this review, the main results of those studies are summarized and discussed together with current knowledge of hydrogen-related defects. The formation of vacancy-hydrogen complexes coupled to a plastic strain localization which is large enough to lead to hydrogen-enhanced vacancy clustering during the plastic deformation appears to be the likely factor that triggers the hydrogen embrittlement of bcc(alpha-) and fcc(gamma)-iron.