Creep behavior and creep-oxidation interaction of selective electron beam melted Ti–48Al–2Cr–2Nb alloy at different temperatures

Abstract

In this work, creep behavior and creep-oxidation interaction behavior of Ti–48Al–2Cr–2Nb alloy fabricated by selective electron beam melting at different temperatures were investigated in detail. This alloy exhibits a near-γ microstructure composed of coarse/fine mixed equiaxed grains. Creep test results show that creep behavior of this alloy is sensitive to temperature. This is mainly manifested in that creep life reduces significantly by 84.8 % as temperature increases from 800 °C to 850 °C. During creep, discontinuous dynamic recrystallization characterized by grain nucleation and growth and continuous dynamic recrystallization characterized by strain gradient and orientation accumulation occur simultaneously. The formation of mechanical twins plays an important role in stimulating dynamic recrystallization. Meanwhile, creep deformation and fracture mechanisms of this alloy at different temperatures were also discussed. On the other hand, oxidation test results reveal that the applied tensile stress has a positive effect on the oxidation behavior of this alloy: the growth of TiO2 oxide is inhibited and the oxidation rate is slowed down. However, under creep-oxidation interaction, the intergranular cracking of the oxide film occurs along with the necking of the alloy matrix during creep.