Low-cycle fatigue behavior and life-prediction model of high-manganese twinning-induced plasticity steels with different loading orientations, pre-strains, and ambient temperatures

The low-cycle fatigue behavior of high-manganese twinning-induced plasticity (TWIP) steel is examined for specimen axial orientations of 0°, 45°, and 90° relative to the rolling direction at a temperature of 449 K. The study aims at a total strain amplitude range (Δε/2) of 0.6 % to 2.4 %, considering both pre-deformed (P-type) and non-pre-deformed (F-type) loading conditions. The fatigue behavior is compared to our recent work at room temperature (295 K, Song et al. Int J Fatigue 2023), to obtain a more comprehensive analysis of the varying deformation mechanisms with different temperatures. Experimental results show that elevated temperature significantly increases the ductility of the material while reducing its strength. Applying a severe plastic pre-strain at high temperature (449 K) will dramatically decrease fatigue life, which is markedly different from the behavior at room temperature. All these characteristics are related to the loading orientations and strain amplitudes.

Additionally, a life-prediction model for high-Mn steel that considers different deformation mechanisms at varying temperatures is also proposed. The model demonstrates fatigue life predictions across 77 loading cases, encompassing five orientations, seven strain amplitudes, three types of loading modes, and two temperatures. The comparison of experimentally and analytically determined lives shows the comprehensive descriptive capacity of the proposed model.