Effects of temperature and stress ratio on cyclic creep behavior of carbon-doped TiAl alloys

In this study, monotonic creep and stress-controlled cyclic creep experiments were conducted on Ti-43Al-6Nb-1Mo-1Cr-0.5C (TAC) alloy under various loading conditions to investigate the cyclic creep deformation and damage mechanisms. The results demonstrate that TAC alloy exhibits a nearly lamellar microstructure, consisting of lamellar colonies and blocky B2 and γ phases at the colony boundaries. TAC alloy exhibits a cyclic creep retardation behavior, characterized by a lower minimum envelope strain rate and a longer rupture life than those in monotonic creep. This retardation behavior is determined by the competing effects of anelastic recovery effect and primary creep regeneration effect. Primary creep regeneration effect significantly increases creep strain and creep damage, while anelastic recovery effect can recover a portion of creep strain and reduce creep damage. Primary creep regeneration effect is strongly affected by anelastic recovery effect. Furthermore, cyclic creep deformation is dominated by dislocation motions. Meanwhile, Ti₂Al particles, which exhibits dislocation pinning effects, precipitate within the B2 phase and at B2/γ interface. This dislocation pinning effect becomes more pronounced at higher temperature. These findings promote a comprehension of the macroscopic response and the microscopic deformation and damage mechanisms associated with the cyclic creep behavior of TiAl alloys.