On the formation of interstitial — Hydrogen clusters in iron

Abstract

The results of a study of the interaction of H with C and N interstitial solutes in high purity Fe using the technique of magnetic disaccommodation are reported. This method, which is the magnetic analog of the better known internal friction methods, has the sensitivity to allow the study of these intersititial solutes at the ppm (atomic) concentration level. The Fe used in these experiments had a total impurity concentration of less than 100 ppm impurities (by spark source mass spectroscopic analysis) reduced by purification in wet and dry hydrogen atmospheres to less than one ppm as measured by the magnetic disaccommodation method. In these pure specimens, containing about 10 ppm H, only low temperature relaxations in the temperature range 4-40 K which were due to hydrogen clusters were observed. The addition of 50 ppm C solutes to these Fe-H specimens reduced the relaxation amplitudes of these H cluster relaxations and introduced a new low temperature relaxation which was identified as resulting from the tunneling of H around a C interstitial. The addition of 200 ppm of N interstitials to the solid solution completely removed the H cluster relaxations without introducing any new relaxations in the temperature range 4-300 K.more » These observations were interpreted as resulting from the trapping of H interstitials by C and N interstitaials.« less