Tailoring the microstructure and mechanical properties of superaustenitic stainless steel by cold rolling and recrystallization annealing

The effects of cold rolling, subsequent continuous heating, and aging on the microstructure and tensile properties of AISI 904L superaustenitic stainless steel were investigated. During cold rolling, the austenite phase showed high mechanical stability against the deformation-induced martensitic transformation. However, work-hardening during cold deformation manifested itself into high strength and reduced ductility for the material during subsequent tensile testing. Upon continuous heating to hot temperatures, the cold worked sample started to recrystallize, and as a result, a fine recrystallized microstructure with an average grain size of 3.5 μm and fine Cr–Mo-rich σ-phase precipitates were obtained for the sample heated up to 925 °C. Heating up to higher temperatures led to the coarsening of austenite grains and the dissolution of the σ-phase. Grain refinement during thermomechanical processing significantly improved the yield stress, as expressed by the Hall–Petch (HP) relation. However, precipitation of the intragranular σ-phase led to deviations from the HP-relation, reflected in enhanced yield stresses or different slopes. Moreover, the formation of the σ-phase during aging adversely affected the elongation to failure.