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Severe plastic deformation is the most efficient method of refining the material structure and producing submicro- and nanocrystalline materials with a unique combination of strength and ductility properties due to a fragmented structure. Upon reaching a definite deformation rate, the fragmentation process is evolving, i.e. a volume of original polycrystalline grains (or monocrystal volume) is broken into mutually disordered areas (fragments). Main methods used to achieve high deformation rates resulting in a visible grain refinement with no sample destruction are equal channel angular pressing and twist extrusion. However, due to rather small finished products, such methods are hardly suitable to produce large-sized structural metal materials, such as, for example, narrow strips. Thus, in recent years highly efficient methods of producing ultrafine-grained materials by asymmetric rolling are widely applied. A fundamental difference between asymmetric and conventional sheet rolling is monotonic deformation in conventional rolling and non-monotonic deformation in asymmetric rolling. Asymmetric rolling in a single deformation schedule combines the processes of rolling (achieved mainly due to a translation component of deformation) and shear (by the rotational deformation). This paper describes the production of narrow strips with an ultrafine-grained structure by asymmetric rolling using L63 alloy grade as an example. Task-specific asymmetry of the process is achieved by mismatching circumferential speeds of rolls, when cold rolling is performed with high contract friction and high single deformations. The scanning electron microscopy was used to study the structure of the samples: before and after asymmetric rolling. It is shown that the deformation by asymmetric rolling with mismatching circumferential speeds of rolls amounting to 50 % and a total percentage reduction of about 70 % results in a fragmented structure and higher performance of the rolling mill due to a reduction in a number of passes, when rolling brass narrow strips from 0.80 to 0.24 mm thick.
Keywords: Asymmetric rolling, severe plastic deformation, brass strips, microstructure© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.