The enhancement of low cycle fatigue life by carbon addition in lamellar TiAl alloy

Total strain range controlled low cycle fatigue tests with lamellar TiAl and TiAl–0.3at.% C alloys were conducted at 800 °C in order to investigate the effect of carbon addition on low cycle fatigue property. It is observed that carbon addition increases fatigue life with increased peak stress and decreased plastic strain range values. Because carbon addition has been reported to change the microstructure, the reason for the enhancement of low cycle fatigue life by carbon addition is investigated in terms of microstructural change. The experimental results clearly indicate that carbon addition inhibits the formation of grain boundary γ phase by reducing the lamellar spacing. Because the grain boundary γ phase is proved to be the region in which the plastic deformation is concentrated and intergranular crack is initiated, it is confirmed that carbon addition increases the fatigue life by inducing uniform plastic deformation and transgranular cracking.