Surface observation and measurement techniques to study the fatigue damage micromechanisms in a duplex stainless steel

The present work presents the contribution of various experimental techniques to study the low-cycle fatigue damage micromechanisms in a duplex stainless steel at room temperature. Surface damage observations are performed in real-time with an in situ microscopic device during a low-cycle fatigue test allowing to follow the development and localization of the plastic slip markings. An interferometric profilometer allows to characterize the morphology of the slip markings with surface relief measured at the end of the test. Moreover, a crystallographic description of the cyclic plasticity completes the surface damage analysis by the identification of slip systems activated in each grain in each phase from SEM and optical photographs and EBSD measurements. Finally, displacement and strain fields on the microstructural scale calculated using digital image correlation technique from surface images taken during cycling explains from a qualitative and quantitative point of view the observed micromechanisms.