NANOCRYSTALLINE STRUCTURE OF NONEQUILIBRIUM FE-CU ALLOYS OBTAINED BY SEVERE PLASTIC-DEFORMATION UNDER PRESSURE

The nanocrystalline structure and non-equilibrium solid solutions of F e-20 at% Cu and Fe-80 at% Cu have been observed after severe plastic d eformation by shear under pressure. The structure of the deformed samp les was studied by electron microscopy, X-ray diffraction and nuclear gamma resonance (NGR) methods. The coarse-grain Fe-Cu alloys were tran sformed into the fine-grained state during straining up to epsilon = 5 -6. Further strain up to epsilon = 7 can be considered as a cold force d superplastic deformation without change of the grain sizes. Accordin g to X-ray and NGR data, a redistribution of atoms and formation of no n-equilibrium solid solutions are the result of strain from epsilon = 5-6 to epsilon = 7. Based on grain rolling, a mechanism of superplasti c deformation has been proposed. Fast diffusion during cold plastic de formation is conditioned by the high stresses acting on the grain boun daries and the volumes of the fine grains. During deformation of the n anocrystalline Fe-Cu alloys the volume diffusion coefficient ave equal to about D-V = 4.10(-16) cm(2)/sec