A relationship between the characteristics of plastic deformation and the specific features of mechano-dynamic penetration of He into nanocrystalline Fe compressively strained at 4.2K was investigated. Iron samples with a grain size of about 200nm were prepared by the multiple equal-channel angular pressing technique. The samples deformed in giant (6 to 7%) sample-averaged serrations, which amounts to several thousand percent strain in a shear band. The amount of He in samples strained to various degrees was measured, and curves of He extraction from these samples were obtained at 300 to 1400K. At a strain of ~50%, the amount of He built up in a sample was found to be substantially higher (more than hundredfold) than that in samples subjected to lower strains. It was found that an increase in the strain rate gave rise to a strain within a serration (the strain localization was enhanced) and that the amount of accumulated He decreased, most probably, because of the shorter deformation time. The He extraction curves obtained with increasing temperature exhibited several peaks. The temperature positions of some of them were about the same for samples strained to different extents, while the other peaks were characteristic of samples subjected to a specific strain only. The results obtained suggest the existence of He traps of different types, which depended upon the original structure and the magnitude of the strain and differ both in the amount of He they contain and in the temperatures at which He was released from these traps.

Mechanodynamic Penetration of Helium Atoms into Nanocrystalline Iron. O.V.Klyavin, V.I.Nikolaev, B.I.Smirnov, L.V.Khabarin, Y.M.Chernov, V.V.Shpeĭzman: Physics of the Solid State, 2007, 49[9], 1666-71