A novel processing route of cold rolling and reversion annealing for enhanced mechanical properties has been investigated in metastable 17Cr-7Ni-type austenitic stainless steels, i.e., commercial grades AISI 301LN and AISI 301, and in some experimental heats. The investigation was essentially aimed at studying the possibility of processing nano/submicron-grained structure in these steels and to rationalize the possible effects of alloying elements on the reversion mechanisms. The steels were cold rolled to various reductions between 45 and 78 pct to induce the formation of martensite, and subsequently annealed between 600°C to 1000°C for short annealing times (mostly 1 to 100 seconds). Microstructure examinations of the reversion-annealed 301LN steel revealed that an ultrafine-grained austenitic structure was formed by the diffusional transformation mechanism within a short holding time above 700°C, even after the lowest cold-rolling reduction. In contrast, in 301 steel and experimental heats, the shear type of transformation occurred at temperatures above 650°C, but fine austenite grains were only formed by recrystallization at higher temperatures or longer holding times, e.g., at 900°C/100 s. An attempt has been made to determine the reversion mechanisms in various steels by modifying the criteria governing the Gibbs free energy change during the martensiteaustenite reversion in Cr-Ni alloys. The room temperature (RT)-tensile property evaluation showed that excellent combinations of yield or tensile strength and elongation are possible to achieve, depending mainly on annealing conditions both in the 301LN and 301 steels, but the experimental heats were too unstable for high ductility. Ultrafine grain size of austenite contributed to this in 301LN and shear-transformed high-dislocated austenite in 301. Upon reversion annealing, the reversion mechanism did not affect the texture. The texture of the reverted fine-grained austenite is very strong compared to the typical texture of commercially cold-rolled and annealed 301LN steel.

An ultra-fine-grained AISI 301LN austenitic stainless steel has been achieved by heavy cold rolling, to induce the formation of martensite, and subsequent annealing at 800°C, 900°C, and 1000°C, from 1 to 100 seconds. The microstructural evolution was analyzed using transmission electron microscopy and the yield strength determined by tension testing. Ultra-fine austenite grains, as small as~0.54 lm, were obtained in samples annealed at 800°C for 1 second. For these samples, tensile tests revealed a very high yield strength of~700 MPa, which is twice the typical yield strength of conventional fully annealed AISI 301LN stainless steels. An analysis of the relationship between yield strength and grain size in these submicron-grained stainless steels indicates a classical Hall-Petch behavior. Furthermore, when the yield dependence on annealing temperature is considered, the results show that the Hall-Petch relation is due to an interplay between fine-grained austenite, solid solution strengthening, precipitate hardening, and strain hardening.

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Austenitic stainless steels possessing good corrosion resistance have recently found growing applications as a constructional material. In this instance, increasing strength properties, which are typically quite low, is of great interest. Due to the low stacking fault energy, strain hardening of alloyed austenite is efficient for increasing tensile strength without impairing ductility seriously. In addition, certain grades are unstable, so that cold working creates strain‐induced martensite that enhances strengthening. Grain size refinement to micrometer scale or even finer can also increase the yield strength, still providing good ductility. In the present paper dislocation and phase transformation strengthening and thereby properties achievable in temper rolled austenitic stainless steels are discussed. Strengthening by the reversion annealing is also described and excellent results achievable are shown. Finally, the effect of bake hardening through the static strain ageing is presented. Long‐term research work in various projects indicates that the current knowledge of strengthening of austenitic stainless steels is close to the industrial utilisation.