Structural Transformations in Duplex Stainless Steel CF8 Under Intensive Cold Plastic Deformation

The austenitic-martensitic transformation in austenitic-ferritic duplex stainless steel CF8 subjected to cold plastic deformation with a deformation degree epsilon = 10-95% is studied here using transmission M & ouml;ssbauer spectroscopy (MS), conversion electron M & ouml;ssbauer spectroscopy (CEMS), and X-ray diffraction (XRD) methods. It is assumed that the alpha '-martensite phase appeared at epsilon > 10%. The CEMS results showed that the formation of alpha '-martensite occurred most intensively in the near-surface layers of the steel, distributing in depth with the growth of the deformation degree. The volume fraction of the alpha '-martensite was determined based on the results of calculations carried out via the MS and XRD methods, and a good correlation was observed. A modified Olson-Cohen model was proposed to determine the dependence of the amount of alpha '-martensite on the deformation degree epsilon. The coefficients included in the Olson-Cohen expression were found.