Effect of strain amplitude on the low-cycle fatigue behavior of a new Fe-15Mn-10Cr-8Ni-4Si seismic damping alloy

The low-cycle fatigue (LCF) properties and post-fatigue microstructure of a Fe-15Mn-10Cr-8Ni-4Si austenitic alloy were investigated under an axial strain control mode with total strain amplitudes, Delta epsilon(t)/2, ranging from 2.5 x 10(-3) to 2 x 10(-2). The fatigue resistance of the alloy was described by Coffin-Manson's and Basquin's relationships, and the corresponding fatigue parameters were evaluated. In addition, the Masing behavior, which is associated with a constant deformation mode during fatigue, was revealed at the examined strain amplitudes. Microstructural observations of the fatigue fractured samples showed that the strain induced epsilon-martensitic transformation accompanied by a planar slip of the Shockley partial dislocations in the austenite is the main deformation mode controlling the fatigue behavior of the studied alloy at Delta epsilon(t)/2 < 2 x 10(-2). However, at Delta epsilon(t)/2 = 2 x 10(-2), the formation of a cell structure was found in the austenite in addition to epsilon-martensitic transformation. The LCF resistance of the alloy was compared with conventional Cr-Ni austenitic stainless steels, ferrous base TRIP and TWIP steels and low yield point damping steels. It was found that at the studied strain amplitudes the alloy possessed a higher LCF resistance compared to conventional Fe-base alloys and steels. Remarkably, the fatigue ductility coefficient, epsilon(f)', of the studied alloy is 1.3-6 times higher than that of the stainless steels because of a cyclic deformation-induced epsilon-martensitic transformation. The results showed that the epsilon-martensitic transformation that occurred in the studied alloy during LCF is the main reason for the improved LCF resistance. (C) 2016 Elsevier Ltd. All rights reserved.