Low-cycle fatigue behavior of HAYNES® HR-120® alloy

Low-cycle fatigue behavior of the HAYNES HR-120 alloy in the temperature range from 24°C to 982°C and total strain range from 0.4% to 2.3% was investigated under an axial total strain control mode in laboratory air. It was noted that increasing temperature generally led to a substantial decrease in the fatigue life of the alloy. It was found that the alloy could exhibit cyclic strain hardening or softening, which was closely related to the imposed total strain range and testing temperature. The microstructural evolution due to low-cycle fatigue deformation was characterized using optical, scanning-electron, and transmission-electron microscopy. It was observed that the precipitation of second-phase particles would occur at or above 761°C. The presence of these precipitates could be taken into account the greater the cyclic-hardening behavior and the reduction of fatigue life, with increasing temperature. In addition, strain fatigue parameters were determined at different temperatures, based on Coffin–Manson and Holloman equations.