AFM and EBSD combined studies of plastic deformation in a duplex stainless steel

In situ tensile tests have been carried out with an atomic force microscope (AFM) to observe plastic deformation of an austenitic–ferritic duplex stainless steel (Uranus 50). The images show that, for austenite grains, parallel equidistant steps corresponding to the emergence of slip planes appear at the surface of the specimen for a low level of strain. For a high level of strain, slip lines with different orientations are distributed homogeneously within all the austenite grains whereas only a few signs of plastic deformation are visible in ferrite grains. After deformation, electron back scattered diffraction (EBSD) method has been used to determine the crystallographic orientations of austenite and ferrite grains on the areas observed by AFM. The combination of AFM and EBSD studies allows to obtain a complete identification of activated slip systems observed on the AFM images. It gives a deep insight on deformation processes in a duplex stainless steel (Burgers vectors, number of dislocations per steps, …). The plastic deformation of ferrite grains is discussed in terms of slip induced by the dislocation accumulation in the neighbouring austenite grains.