Behavior of the helium in metals and the problem of helium induced brittleness in stainless steels

The representative works from an extensive literature on the helium in metals are reviewed. The status of researches in this field is summarized with an emphasis on the states of helium atoms in metals, their microscopical distribution and migration, and also their macroscoptical effects. The problem of the helium induced brittleness in stainless steels is particularly discussed. Some relevant experimental results obtained by authors are also included as examples