The production of nanostructural materials is an important part of modern nanotechnology. The application of SPD technology is a necessary condition for the production of nanomaterials with specific properties. The idea of in-situ SPD technology consists in the continuous registration of external deformation parameters and the establishment of its relation with the internal nanostructural parameters.
The in-situ SPD technology of producing nanostructured materials is realized by plastic torsional deformation and pure shear deformation under high pressure. This technology provides in-situ method of deformation and formation nanocrystalline structures. Simultaneously, structure - sensitive parameters (such as, electricalresistance, acoustic emission) were investigated during the severe plastic deformation. In addition the direct X-ray (XRD and SAXS methods) study of the structural evolution was performed continuously during both compressive and shear deformation.
It is shown, that the plastic deformation of austenite of high-nitrogen steels (with CN=0.06ё0.57%N) in the fragmentation stage is accompanied by structural changes. This promotes the formation a nanocrystalline structure.
The in-situ SPD technology of producing the materials with submicro- and nanocrystalline structure by shear under high pressure is developed. The fragmentation and phase (g«a) transformation under high pressure and shear deformation is accompanied by structural modifications in the austenite of high-nitrogen steels. This promotes the shaping of complex parts with a nanocrystalline structure.
The application of in-situ SPD technology has made it possible to identify three stages of formation of NC structures by finding functional correlation between the critical shear stress and the start of plastic flow.
The interrelation was established between the external parameters (critical shear stress; stress at the initiation of plastic flow) and microstructural parameters (grain size, q
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