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The aim of the present review is to summarize the recent achievements in the development of ultrafine-grained austenitic/ferritic stainless steels processed by large strain deformation. Various aspects of microstructure evolution and its effect on the properties of processed steels are considered. The paper starts from an overview of various methods of large strain deformation that are successfully used for producing ultrafine-grained metallic materials. Then, the structural mechanisms responsible for grain refinement during plastic deformation are considered and discussed from the viewpoint of their efficiency and effect on the subsequent recrystallization behavior. Finally, some physical and mechanical properties of ultrafine-grained stainless steels are observed. It is concluded that the development of ultrafine-grained microstructures during severe plastic deformation results from a kind of continuous dynamic recrystallization. Namely, the misorientations among the strain-induced cells/subgrains progressively increase up to typical values of ordinary grain boundaries. Following the rapid reduction at relatively small strains, the deformation grain size gradually approaches its final value, which depends on alloying/phase content and processing conditions. An increase in the number density of interface/grain boundaries in the initial state significantly accelerates the kinetics of grain refinement during subsequent plastic working. [ABSTRACT FROM AUTHOR]

The microstructure/texture evolution and strengthening of 316 L-type and 304 L-type austenitic stainless steels during cold rolling were studied. The cold rolling was accompanied by the deformation twinning and micro-shear banding followed by the strain-induced martensitic transformation, leading to nanocrystalline microstructures consisting of flattened austenite and martensite grains. The fraction of ultrafine grains can be expressed by a modified Johnson-Mehl-Avrami-Kolmogorov equation, while inverse exponential function holds as a first approximation between the mean grain size (austenite or martensite) and the total strain. The deformation austenite was characterised by the texture components of Brass, {011}<211>, Goss, {011}<100>, and S, {123}<634>, whereas the deformation martensite exhibited a strong {223}<110> texture component along with remarkable γ-fibre, <111>∥ND, with a maximum at {111}<211>. The grain refinement during cold rolling led to substantial strengthening, which could be expressed by a summation of the austenite and martensite strengthening contributions. [ABSTRACT FROM AUTHOR]