LCF Behaviour of Ultrafine Grained 301LN Stainless Steel

Cyclic strain behaviour of metastable austenitic 301LN steel with different grain sizes – coarse (14 μm) and ultrafine (1.4 μm) grained – produced by the special thermo-mechanical treatment based on the martensite-to-austenite reversion was investigated. Low-cycle fatigue (LCF) tests were conducted on flat specimens at room temperature in fully push-pull mode under strain control with constant strain rate of 2×10–3 s–1 and constant total strain amplitude ranging from 0.4% to 0.9%. LCF behaviour was characterised by cyclic hardening/softening curves and fatigue life curves. After completion of fatigue tests surface fatigue damage was studied using scanning electron microscopy (SEM). Ferritoscope was adopted to reveal the destabilization of austenitic structure and evaluate the extent of deformation induced martensitic transformation.