One of the authors, Yu Ivanisenko, is thankful to DFG for funding support of a part of this investigation. The authors (A. Ganeev, R. Valiev, and M. Murashkin) are thankful to RFBR -11-08-91330 for partial support of the investigation.Grain boundary (GB) segregations were investigated by atom probe tomography in an Al-Mg alloy, a carbon steel and Armco 1 Fe processed by severe plastic deformation (SPD). In the non-deformed state, the GBs of the aluminum alloy are Mg depleted, but after SPD some local enrichment up to 20 at% was detected. In the Fe-based alloys, large carbon concentrations were also exhibited along GBs after SPD. These experimental observations are attributed to the specific structure of GBs often described as ''non-equilibrum'' in ultra fine grained materials processed by SPD. The GB segregation mechanisms are discussed and compared in the case of substitutional (Mg in fcc Al) and interstitial (C in bcc Fe) solute atoms. 968 wileyonlinelibrary.com ß

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The paper presents the results of a study on the microstructure and mechanical properties of a mediumcarbon steel (0.45 % C) processed by severe plastic deformation (SPD) via high-pressure torsion (HPT). Martensite quenching was first applied to the material, and then HPT processing was conducted at a temperature of 350°C. As a result, a nanocomposite type microstructure is formed: an ultrafine-grained (UFG) ferrite matrix with fine cementite particles located predominantly at the boundaries of ferrite grains. The processed steel is characterized by a high-strength state, with an ultimate tensile strength over 2500 MPa. Special attention is given to analysis of the thermal stability of the microstructure and properties of the steel after HPT processing in comparison with quenching. It is shown that the thermal stability of the UFG structure produced by HPT is visibly higher than that of quenchinginduced martensite. The origin of the enhanced strength and thermal stability of the UFG steel is discussed.