Stability of the Ultrafine-Grained Structure of Austenitic Corrosion-Resistant Steels during Annealing

Abstract

This work focuses on the stability of the ultrafine structure in austenitic corrosion-resistant steels, such as AISI 304L (0.05 C–18.2 Cr–8.8 Ni–1.7 Mn–0.4 Si (wt %) and Fe for balance) and AISI 316L (0.04 C–17.3 Cr–10.7 Ni–1.7 Mn–0.4 Si–2 Mo (wt %) and Fe for balance) during annealing at 700°С. The ultrafine-grained structure has formed in the steels under study during rolling at 200°С due to the development of strain twinning and microshear bands. Annealing after the rolling results in continuous recrystallization and grain growth. Steel 316L has higher stability to grain growth than steel 304L, especially during annealing in the range 30–480 min. Grain growth in 316L steel during prolonged annealing is accompanied by precipitation of the Laves phase. The ultrafine-grained structure with grain size less than 1 μm is retained in 316L steel after annealing for 480 min. Grain growth during annealing is accompanied by softening of both steel grades.