Abstract:Ti-47.5Al-6.8Nb-0.2W-xY (x=0,0.1,0.2, at%) alloys were prepared by high-energy ball milling and spark plasma sintering processes, and the effects of Y microalloying on the high-temperature compression creep properties of Ti-47.5Al-6.8 Nb-0.2W alloys were investigated by SEM, EBSD and TEM. Creep experiments were carried out at 800–850 ℃, with a stress of 250 MPa and a time of 50 h. The results show that the Ti-47.5Al-6.8Nb-0.2W-xY alloys are all composed of equiaxial γ grains, the bulk α2 and B2 phases at γ grain boundaries, and α2/γ lamellar colonies. The added Y mainly exists in the form of Al2Y particles at the grain boundaries to form a chain structure and Y can refine the grains and increase the α2/γ lamellar colonies. When the Y content is increased from 0 to 0.2at%, the grain size is reduced from 12.1 μm to 7.8 μm, exhibiting the most significant refining effect. After creep, γ grains in the alloy are slightly flattened, accompanied by lamellar bending and degradation phenomena, and a large number of fine recrystallized grains and spherical B2 phase appear within the lamellar clusters. Creep temperature increase can promote the formation of dynamic recrystallisation. The addition of Y significantly improves the compressive creep properties of the alloy. At 800 ℃, the maximum creep strain of the 0.2Y alloy is 8.96%, and the steady creep rate is 4.01×10–7 s–1, reduced by 32.83% and 38.31% compared with those of the alloy without Y, respectively. The improvement in the mechanical properties of the alloys is attributed to the precipitation strengthening of the second phase Al2Y particles, lamellar refinement, and reduction of the B2 phase.