Effect of σ-Phase on the Strength, Stress Relaxation Behavior, and Corrosion Resistance of an Ultrafine-Grained Austenitic Steel AISI 321

This paper reported the results of research into effect Equal Channel Angular Pressing (ECAP) temperature and 1-h annealing on mechanical properties, stress-relaxation resistance, corrosion resistance austenitic steel AISI 321L with strongly elongated thin δ-ferrite particles in its microstructure. The formation α′-martensite fragmentation austenite grains takes place during ECAP. Ultrafine-grained (UFG) steels demonstrate increased strength. However, we observed a reduced Hall–Petch coefficient as compared coarse-grained (CG) due to particles. UFG specimens were found have 2–3 times higher CG steels. For first time, high was shown stem from internal mechanism, i.e., interaction lattice dislocations non-equilibrium grain boundaries. Short-time at 600–800 °C result nucleation σ-phase nanoparticles. These nanoparticles affect boundary migration, raise strength, but reduce steel. Lower be related ECAP annealing.