Abstract: Austenitic-ferritic (duplex) stainless steels are successfully used in chemical, nuclear, oil and gas industries, due to their good mechanical properties and excellent generalized and localized corrosion resistance in many environments and operating conditions (for example, chloride induced stress corrosion). The aim of this work is the analysis of the influence of the chemical composition and of the high temperature embrittlement processes in three different duplex stainless steels. Scanning electron microscope (SEM) fracture surface analysis was performed to investigate the fatigue crack propagation micromechanisms.