Besides the advantage that they can be produced in bulk shape, SPD nanometals show a number of particular properties which have not been achieved so far by nanometals produced by other methods. In spite of the advanced strength and fatigue life time they show a considerable ductility and fracture toughness, an increased rate of hydrogen ad- and desorption, and changes in phase boundaries (e.g. increases in solubility of alloying atoms a.s.o.). In principle, all these effects can be related to the existence, interactions and rearrangements of deformation induced lattice defects. While the enhancements of ductility and fracture toughness are caused by distortion-minimizing rearrangements of dislocations, the acceleration in hydrogen diffusion, and especially the changed parameters for the existence of certain phases, seem to be consequences of the presence of deformation induced vacancies. According to recent experiments conducted in SPD nanometals those reach concentrations which are even higher than those known from conventional plastic deformation. These results clearly favour the importance of the extended hydrostatic pressure in SPD deformation, rather than ideas that strong strain gradients being typical of SPD may be responsible for the increased storage of lattice defects in SPD nanometals.

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1. SPD processed alloys as efficient vacancy-hydrogen systems