Deformation and damage mechanisms of a bimodal 12Cr-ODS steel under high-temperature cyclic loading

•Disparity in cyclic deformation behavior due to strain amplitude and temperature was studied in a bimodal ferritic 12Cr-ODS steel.•Steel exhibits Masing behavior at 550°C and minor but a progressive deviation at 650°C.•Dislocation arrangements varied as a consequence of different grains sizes, orientations, and oxide particle distributions.•A propensity towards cross-slip and hence cell structure formation increased with increase in strain amplitude and temperature.•Stages of crack path include stage I and stage II fatigue damage, duration of which is a function of testing conditions.