Hall–Petch Behavior in Ultra-Fine-Grained AISI 301LN Stainless 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 μm, 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.