Abstract: TC20 alloy specimens treated by different heat treatment processes, as well as first initial solution (840 ℃× 0.5 h) and then different aging treatment (460 ℃× 4 h, 320 ℃× 15 min→460 ℃× 4 h, 320 ℃× 10 min, 460 ℃× 10 min) were tested and characterized by SEM, TEM, XRD and hardness tester,and β→αphase transformation of TC20 alloy during α relative aging was studied. The results show that the hot rolled microstructure is composed of α and β phase, and many small α phases are formed in the solid solution structure. The lamellar-distributed α phase in the specimen is formed at 460 ℃ for 4 h, and the α phase with smaller length-width ratio is formed in the specimen when aged at 320 ℃ for 15 min→460 ℃ for 4 h, and most of the size of fine α phases is close to 100 nm. The second phase formed by the two aging methods is α phase, and the α phase with smaller size is obtained at 320 ℃ for 15 min→460 ℃ for 4 h. When the temperature reaches 460 ℃, a multitude of α phase nucleated in the β matrix can be carried out by ω phase, thus formed a dense and uniform distribution. The ω phase in the alloy is no longer exists after 320 ℃ for 15 min→460 ℃ for 4 h treatment, and more α phase is precipitated at the same time. The alloy hardness is up to 503 HV, which is significantly higher than that of β matrix, and the hardness of the alloy can be improved by the precipitation of α phase substantially.

Key words: TC20 alloy, aging, α phase, hardness, microstructure evolution