Abstract
The behavior of hydrogen in austenitic stainless steels with different Ni contents, SUS 27, SUS 32 and SUS 42, is studied by means of the 57Fe Mössbauer effect. By the electrolytic hydrogenation, Mössbauer spectra of these stainless steels show asymmetric tails, broadenings, and positive isomer shifts. The patterns are analyzed and two main spectral components are obtained. One is from the γ-phase iron not affected by hydrogen, and the other is from the iron atoms which are affected by surrounding interstitial hydrogen atoms. The latter shows a positive isomer shift relative to the former and its absorption intensity increases with increasing Ni content. Computer analyses show the two-component distribution of the isomer shift more precisely and qualitatively and, in addition, exhibits a small third component which may arise from iron-nickel hydride. The observed positive isomer shift might be interpreted in such a way that the 3d holes of iron are partially filled by the 1s electrons from solute hydrogen.
The martensitic transformation of the low Ni austenitic stainless steel, SUS 39, is also studied. Additional broad and ferromagnetic pattern, arising from the α-phase, has an internal field of about 260 kOe at room temperature. The amount of the α-phase increases linearly with the charging time up to 20 hr. This result suggests that the transformation advances into the interior of the specimen at a constant rate.
