Investigation of nanoscale strains at the austenitic stainless steel 316L surface : Coupling between nanogauges gratings and EBSD technique during in situ tensile test

Abstract : The understanding of the mechanical properties at the microstructure scale is a key factor for the material macroscopic behavior comprehension and its appropriate engineering at the scale of the structure. In this study, a new approach which is based on the combination of both nanogauges displacements monitoring and electron backscatter diffraction (EBSD) techniques performed under Scanning Electron Microscope (SEM) during in-situ tensile tests is proposed. Strain evolutions at the microstructure components and the behavior of the material can be compared to the crystallographic data. The approach was applied to austenitic stainless steel 316L specimen in order to bring a proof of concept and put into evidence its potential. Among the information of interest which can be obtained through this technique, one can cite the possibility to highlight the strain initiations in the vicinities of twins and their evolutions during the tensile test or to evidence the strain heterogeneities at the surface of the specimen and its influence over the elongations and rotations of the microstructure components, which tends to be reorganized in order to balance the mechanical stress. Besides, such heterogeneities can be expressed in terms of misorientations and quantified from the EBSD data. The twinning and slip activities can also be correlated to the hardening of the material thanks to this method of characterization. As for its interest for characterizing the plastic domain, the technique can show how some grains may activate more than one slip system. Finally, it has been here demonstrated how complementary and powerful the combination of these two techniques may be considered and how it may give access to a better understanding of the material microstructure properties.