Determination of the room-temperature cyclic stress-strain curve of AISI 304LN austenitic stainless steel by two different methods

A comparison is made between the companion specimen test (CST) and the incremental step test (IST) methods for determining the cyclic stress-strain curve of AISI 304LN stainless steel at room temperature. Only seven blocks were needed for obtaining a stable pattern in the IST. Also, Masing behaviour was seen only when this testing procedure was used. In both types of test, during room-temperature low-cycle fatigue deformation the metastable AISI 304LN stainless steel underwent a martensitic transformation. In the CST secondary hardening was observed in specimens tested at and above a strain amplitude of ±0.85% and this could be attributed to martensite formation. Two martensite phases formed: an ε-martensite (h.c.p) and an α′-martensite (b.c.c). The dislocation arrangement in the IST resembled that present in the specimens tested at higher strain amplitudes in the CST. © 1992.