Cyclic deformation behaviors of Ti-46Al-2Cr-2Nb-0.15B alloy during thermo-mechanical fatigue tests

Thermo-mechanical fatigue tests were carried out on the gamma-TiAl alloy in the temperature range of 500-800 °C under mechanical strain control in order to evaluate its cyclic deformation behaviors at elevated temperature. Cyclic deformation curves, stress-strain hysteresis loops under different temperature-strain cycles were analyzed and dislocation configurations were also observed by TEM. The mechanisms of cyclic hardening or softening during thermo-mechanical fatigue (TMF) tests were also discussed. Results showed that thermo-mechanical fatigue lives largely depended on the applied mechanical strain amplitudes, applied types of strain and temperature. On the hysteresis loops appeared two apparent asymmetries: one was zero asymmetry and the other was tensile and compressive asymmetry. Dislocations configuration and slip behaviors were contributed to cyclic hardening or cyclic softening.