Martensitic transformation induced by cold deformation of lean duplex stainless steel UNS S32304

Lean duplex UNS S32304 is an austenitic ferritic stainless steel with pitting resistance equivalent number around 24-25. Its corrosion resistance is similar to AISI 316L steel, but with the advantage of a yield limit two times superior to conventional austenitic grades. Deformation induced martensitic transformations (γ→ε and γ→ α') have been extensively studied in austenitic steels, but few works were published about these reactions in austenitic ferritic grades. In the present work, deformation induced martensitic transformation in lean duplex UNS S32304 was investigated by means of magnetic measurements and X-ray diffraction. The curves of α' martensite volume fraction against true deformation by cold rolling were constructed and compared to duplex and austenitic grades. It was found that lean duplex UNS S32304 is much more susceptible to martensitic transformation than duplex UNS S31803, which can be explained by its lower Mo and Ni contents.