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Information × Registration Number 0200U004492, 0196U018997 , R & D reports Title The research of physical nature of hydrogen embrittlement in iron-based alloys popup.stage_title Head Gavrylyuk Valentyn Gennadijovych, Registration Date 24-07-2000 Organization Institute for metal physics NAS Ukkraine popup.description2 FCC iron alloys (stainless austenitic steels) were used as the subject of investigation. The aim of the research is an investigation of the physical nature of hydrogen embrittlement of iron alloys and the elaboration of practical recommendations for the creation of hydrogen-resistant steels. Electron spin resonance, nuclear gamma resonance (Mossbauer spectroscopy), X-ray phase analysis, transmission electron microscopy, internal friction, positron annihilation and mechanical tests were used as the methods for investigation. The effect of hydrogen on the electronic structure of FCC iron alloys was investigated. The considerable increase of the concentration of conductive electrons and, simultaneously, intensification of the exchange interaction of free electrons with localized d-electrons for hydrogen saturation were estimated. If the distance between hydrogen atoms is less than characteristic dimension of the polarization scale of conductive electrons, the electrons, introduced with hydrogen, would pl ay a part in a junction between the nickel enriched super paramagnetic clusters and cause a ferromagnetism by means of the exchange interaction, for the enough hydrogen concentration. The hydrogen raise of the Debye temperature in austenitic steels, i.e. the decrease of an amplitude of vibrations of metal atoms, and consequently, for the Debye approximation, non- softening of inter atomic bond was estimated. The nature of the hydrogen induced phase transformations was investigated. The only hydrogen induced phase was indicated to be HCP one. The possible mechanism of HCP- phase precipitation consists in hydrogen enhancing of the equilibrium vacancies concentration, that destabilize FCC lattice. There was estimated, that HCP-phase does not precipitate at high hydrogen pressure, whereas the embrittling hydrogen effect is maintained. The decreasing of start stresses of dislocation sources for hydrogen saturation and acceleration of the dislocation mobility are estimated. It is coordinated with hypothesis of hyd rogen embrittlement based on the localization of plastic deformation by hydrogen. The body of yielded results enables conclude, that the nature of hydrogen embrittlement consists in strengthening the metallic component of the inter atomic bond by hydrogen, that facilitates to local lattice softening in the spots of hydrogen accumulation, early start of dislocation sources and localization of plastic deformation, resulting in pseudo-brittle micro destruction. The practical recommendation, following from the yielded results, is modification of iron alloys with elements, raising the migration enthalpy of hydrogen in FCC- lattice. The composition of enhanced hydrogen resistant stainless austenitic steel was offered. Product Description popup.authors popup.nrat_date 2020-04-03 Close