Abstract:In this paper, the low-cycle fatigue behavior of Ti-6Mo-5V-3Al-2Fe-2Zr alloy under two different heat treatment processes of solution + isothermal aging and solution + furnace cooling was studied. The results show that the microstructure of M1 alloy after solution + isothermal aging treatment contains short rod-like intracrystalline α phase and continuous grain boundary α phase, The microstructure of M2 alloy obtained after solid solution + furnace cooling treatment contains elongated acicular intragranular α phase, continuous grain boundary α phase and WGB α phase. M1 and M2 alloys exhibit cyclic stability at low strain amplitudes of 0.6 %, 0.7 % and 0.8 %, and M2 alloys exhibit higher stress amplitudes with smaller intracrystalline α phase spacing. At a high strain amplitude of 1.0 %, due to the competitive mechanism of back stress and friction stress, both M1 and M2 alloys exhibit cyclic softening. Under high strain amplitudes of 0.9 % and 1.0 %, the back stress hardening rate of M2 alloy is relatively small, the cyclic softening phenomenon is more obvious, and the stress amplitude is relatively low. The intracrystalline α phase of M2 alloy divides the matrix into several " closed units " and forms a WGB α phase parallel to the intracrystalline at the β grain boundary, resulting in lower low cycle fatigue life than M1 alloy.