超温热暴露对铸造TiAl-4822合金显微组织和力学性能的影响OA

This work investigates the alterations in the microstructure and mechanical properties of the Ti-48Al-2Cr-2Nb alloy(referred to as 4822 alloy)following simulated short-term superheated service at 800-950℃.The research focuses on the effects of thermal exposure temperature and holding time on the microstructure,room-temperature and high-temperature tensile properties,and high-temperature endurance properties of 4822 alloy.The results reveal that after exposure at 800-950℃,the α2 phase within theα2/γ lamellar colonies dissolves,forming coarse γ lamellae.As the thermal exposure time increases,the dissolution of the α2 phase becomes more pronounced,the ends of the α2/γ lamellar structures coarsen,and the lamellae grow into adjacent colonies.After treatment at 900℃,spherical B2 precipitates form at the boundaries between lamellar colonies and equiaxed γ grains.At 950℃,fine B2 precipitates appear within the coarse γ lamellae inside the colonies,and the number of B2 precipitates increases.Prolonging the exposure time leads to the precipitation of extremely fine γ lamellae within blocky α2 phases,with their quantity increasing;equiaxed γ grains at colony boundaries gradually grow,and the number of equiaxed γ grains within the colonies also rises.After thermal exposure at 850℃/10 min,850℃/120 min,and 900℃/10 min,both the room and high-temperature yield strengths of the alloy increase,while the room and high-temperature elongations decrease.However,after thermal exposure at 950℃/10 min,the room-temperature elongation of the alloy is(2.4±0.55)%,representing an increase of 5.73%compared to its original state.After thermal exposure at 850℃/10 min,850℃/120 min,and 900℃/10 min,the stress rupture lives of the alloy under both 650℃/400 MPa and 700℃/350 MPa conditions are extended.However,after thermal exposure at 850℃/120 min,the stress rupture life under 650℃/400 MPa is(14.85±3.55)h,which decreased by 94.02%compared to its original state.