Cyclic deformation of duplex Fe-30Mn-10Al-0.4C alloy at room temperature

Duplex (a + γ) FeMnAlC alloy was cyclically strained at room temperature. The cyclic stress responses and stress-strain curve were examined. In the region of low strain amplitudes, this duplex alloy cyclically softened as a result of the localization of the plastic deformation in the austenitic phase which cyclically softened. However, the existence of the ferritic phase which was considered to exhibit cyclic hardening did not offset the softening. In the region of high strain amplitudes, very rapid cyclic hardening was observed. Examination of the surfaces of the fatigued specimens revealed that microcracks mainly nucleate in the austenitic phase in regions of low strain amplitudes. As the specimens were subjected to higher strain amplitudes, microcracks started to nucleate in the ferritic phase and became predominant. It is believed that, when the ferritic phase is ready to accommodate the plastic deformation, rapid hardening occurs and results in the nucleation of the fatigue cracks in the ferritic phase. © 1988.