Mobility of dislocations in the iron-based C-, N-, H-solid solutions measured using internal friction: Effect of electron structure

Highlights: • Carbon in the iron decreases concentration of free electrons, nitrogen and hydrogen increase it. • Carbon in the iron decreases line tension of dislocations, whereas nitrogen and hydrogen increase it. • Effect of C, N and H on strength of S-K relaxation and ADIF is correlated with change in the electron structure. -- Abstract: Effect of interstitial elements on the Snoek-Köster relaxation and the amplitude-dependent internal friction is analyzed in terms of a change in the electron structure. The density of electron states in the bcc and fcc iron doped with carbon, nitrogen or hydrogen has been ab initio calculated paying due attention to that at the Fermi level. It is obtained that nitrogen and hydrogen increase density of states in the both iron phases, whereas the effect of carbon is opposite. In consistency, using electron spin resonance in the fcc iron alloys, the concentration of free electrons is found to be increased due to nitrogen and hydrogen and decreased by carbon. Based on the obtained results, a conclusion about corresponding change in the dislocation line tension controlling mobility of dislocations is derived. This correlation between electron structure and mobility of dislocations is confirmed for the Snoek-Köster relaxation in the bcc iron phase and for the internal friction background, ADIF, in the fcc phase.