Isothermal and thermomechanical fatigue behavior of Ti-2Al-2.5Zr titanium alloy

In-phase and out-of-phase thermomechanical fatigue (TMF) tests in the temperature range of 200-400 degrees C and isothermal fatigue (IF) tests at 400 degrees C were conducted to investigate cyclic deformation behavior and fatigue life of Ti-2Al-2.5Zr alloy. The back stress and the friction stress were extracted, and the internal stress competition mechanism underlying the cyclic hardening/softening behavior was clarified. The fatigue life of TMF and IF exhibited slight differences at strain amplitudes greater than 0.6%, whereas it depended on loading modes at the strain amplitude of 0.4% owing to the increase in the relative deviation in the plastic strain energy density and in the peak stress.