Ti-1300合金等温时效过程中相结构和组织转变

Study on transformation of phase structure and Microstructure for Ti-1300 alloy during isothermal aging

摘要:

采用OM、SEM、XRD和TEM等研究了固溶态Ti-1300合金在350～700℃等温时效过程中相结构和组织转变。结果表明，Ti-1300合金在350℃等温时效时，β相基体上开始弥散析出细小的颗粒状ω相，后期ω相消失，出现了片状的α相。亚稳β相的分解方式为：β→ω+β→α+β。在400℃等温时效1h时，亚稳β相分离出了β′相，继续保温，β′相消失，出现了细片状α相，亚稳β相的分解方式为：β→β′+β→α+β。在500℃~700℃等温时效时，α相在β晶界和晶粒内亚晶界上快速形核，随着保温时间的延长，晶界α相逐渐向晶内生长为α集束，随着时效温度升高，α相的片层越厚；亚稳β相的分解方式为：β→α+β。

Abstract:

The transformation of phase structure and microstructure for solution treated Ti-1300 alloy during isothermal aging between 350～700℃ were investigated using optical microscopy, scanning electron microscopy, X-ray diffraction and transmission electron microscopy analyses. Results show that the fine ellipsoidal ω phase formed in the Ti-1300 alloy at 350℃ firstly, then with the disappearing of ω phase, acicular α phase precipitates formed in the β matrix. The decomposition mechanism of this process was β→ω+β→α+β. The glabol β′ phase separated from the β matrix at 400℃ after 1h. With the increasing of holding time, the β′ phase could be served as the nucleation sites for α phase precipitates, thus leading to acicular α microstructure. And the decomposition mechanism was β→β′+β→α+β. After aging at 500℃~700℃, the decomposition mechanism of metastable β phase became as β→α+β. The nucleation site of the secondary α phase was mainly in the prior β grain boundaries and the internal nucleation of the prior β grain, and the grain boundary α phase with same orientation grew into α cluster gradually. Increasing the aging temperature, the thickness of α plate-like phase increased.