The microstructural changes leading to nanocrystalline structure development and the respective tensile properties were studied in a 304L stainless steel subjected to large strain cold rolling at ambient temperature. The cold rolling was accompanied by the development of deformation twinning and martensitic transformation. The latter readily occurred at deformation microshear bands, leading the martensite fraction to approach 0.75 at a total strain of 3. The deformation twinning followed by microshear banding and martensitic transformation promoted the development of nanocrystalline structure consisting of a uniform mixture of austenite and martensite grains with their transverse sizes of 120–150 nm. The developed nanocrystallites were characterized by high dislocation density in their interiors of about 3 × 10¹⁵ m⁻² and 2 × 10¹⁵ m⁻² in austenite and martensite, respectively. The development of nanocrystalline structures with high internal stresses led to significant strengthening. The yield strength increased from 220 MPa in the original hot forged state to 1600 MPa after cold rolling to a strain of 3.

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}, Goss, {011}, and S, {123}, whereas the deformation martensite exhibited a strong {223} texture component along with remarkable γ-fibre, ∥ND, with a maximum at {111}. The grain refinement during cold rolling led to substantial strengthening, which could be expressed by a summation of the austenite and martensite strengthening contributions.

The change in the grain boundary network during recrystallization and grain growth was studied in a 316L austenitic stainless steel subjected to 5% cold rolling reduction. The primary recrystallization rapidly developed upon heating to 1000 °C, resulting in the development of relatively coarse-grained microstructure with a grain size about 100 μm. The recrystallized microstructures contained large fractions of annealing twins with their ∑3ⁿ SCL boundaries. The latter ones served as interrupters of the ordinary grain boundary network. The fraction of ∑3ⁿ CSL boundaries increased with increasing the grain size during prolonged annealing. On the other hand, the number of interruptions per unit area remained nearly the same during annealing. Hence, the number of interruptions per a grain increased in accordance with a power law function of the grain size with an exponent of 2. The relationships obtained for the grain boundary network evolution can be used to predict the microstructure evolution in austenitic stainless steels during primary recrystallization followed by grain growth.

The ultrafine-grained microstructures and their effect on the yield strength of a 316L-type austenitic stainless steel processed by large strain cold/warm rolling and subsequent annealing were studied. A kind of continuous recrystallization developed during annealing, resulting in the evolution of uniform ultrafine-grained microstructures with relatively high residual dislocation densities. The development of such microstructure at 973 K led to excellent combination of tensile properties including high yield strength (σ_0.2 > 900 MPa) and satisfactory plasticity (δ > 15%). A unique power law function between the annealed grain size and the dislocation density with a dislocation density exponent of −0.5 was obtained for these continuously recrystallized microstructures. A physically justified explanation of the observed structural/substructural strengthening is introduced.