Experimental investigation on anelasticity-controlled cyclic creep behavior in multiscale hybrid-reinforced TiAl alloys

As hot-end components in aero-engines, TiAl alloys are expected to experience cyclic creep in service. In this work, hybrid-reinforced TiAl alloys with superior creep resistance were developed through synergistic micro-alloying of C and Y₂O₃ combined with long-term annealing. Monotonic and cyclic creep tests under various loading conditions were conducted to specifically investigate the cyclic creep behavior of the hybrid-reinforced TiAl alloys. The results indicate that, compared with monotonic creep, cyclic creep exhibits a longer rupture life and a lower strain rate due to anelastic recovery. However, the introduction of cyclic loading enhances the intrinsic creep deformation capacity of TiAl alloys due to primary creep regeneration effect, and accelerates the intrinsic creep damage, resulting in a shorter creep endurance life. Two dominant anelastic recovery mechanisms associated with dislocation cells and dislocation pile-ups were revealed. Moreover, the presence of hybrid reinforcements enhances the anelastic recovery extent. The effects of various loading parameters, including the peak stress dwell time, stress ratio, and temperature, on the macroscopic cyclic creep response were clarified. The microscopic cyclic creep deformation and failure mechanisms, as well as the dynamic precipitation behavior of Ti₂AlC within the B2 phase were elucidated. A comprehensive understanding of cyclic creep behavior from both macroscopic and microscopic perspectives will help advance the structural integrity assessment of TiAl alloys.