Cyclic plasticity and internal dislocation structure in two-phase alloy

Austenitic-ferritic stainless steel has been cycled in symmetrical push-pull regime with constant strain rate and different strain amplitudes. Hysteresis loops were recorded and analysed. The plot of the second derivative of the half-loop vs. relative strain shows one peak for low amplitude straining corresponding to the cyclic deformation of softer phase, austenite. With increasing strain amplitude second peak appears and corresponds to the cyclic deformation of the harder phase, ferrite. Transmission electron microscopy study revealed parallel bands in austenite and initial virgin dislocation structure in ferrite at low amplitude while cell structure in austenite and secondary wall structure in ferrite at high amplitude.