Metastable austenitic stainless steels of the AISI 300 series can undergo a deformation-induced martensitic transformation: the gamma-austenite phase is transformed to epsilon-martensite and alpha'-martensite phases due to plastic deformation. The strain-induced martensitic transformation enhances the work hardening of these SS, and affects their ductility. This transformation is very important in austenitic stainless steels where the induced plastic deformation provides a combination of good mechanical properties, such as formability and strength. The extent of the martensitic transformation these steels can undergo is a function of material composition, processing temperature and strain. Besides, by heat treatments above the As temperature, the austenitic structure can be recovered. However, the difficulty of predicting the material behaviour is one of the major drawbacks of these steels. In order to understand this behaviour it is of great importance to be able to characterize the morphology, crystallography and the amount of different types of phases.

In the present paper, a series of specimens of AISI 316 austenitic SS  were submitted to 30% lamination at a temperature of (-70ºC), to achieve a very high martensite content. The reversion of martensite to austenite was made by means of isochronic, isothermal heat treatments at temperatures between 250 and 800ºC, so as to induce partial martensite-austenite phase transformation. The initial (before reversion treatment) and the final amount of austenite depend on treatment temperature and steel grade. The samples are studied by optical and electronic microscopy; X-ray diffraction; magnetization measurements; and electromagnetic non destructive methods: feritscope, conductivity measurements using Van der Pauw’s technique, and magnetic permeability assessments by an eddy current inverse method.