(西北工业大学 凝固技术国家重点实验室，西安 710072)
摘 要: 对近β型Ti-7333(Ti-7Mo-3Cr-3Nb-3Al)合金在350 ℃进行不同时间的等温时效，结合XRD及TEM分析得出该合金等温在时效过程中的组织演变规律，并采用等温热膨胀分析方法研究ω相变动力学行为。结果表明：Ti-7333合金固溶后淬火获得单一的β组织，350 ℃时效4 h弥散析出细小的颗粒状ω相；经时效8 h后，ω相长大且均匀、弥散分布于β基体中；经20 h时效后，β基体中除含有ω相外，还析出细小的次生α相。同时，ω相聚集成团，造成分布不均匀，且伴随着次生α相的析出，ω相形貌发生变化。这是由于等温时效温度低、淬火得到的不稳定β相未能直接转变成α相，而是通过先生成过渡相ω相再由ω相转变成α相，使得合金相稳定性增加。
关键字: Ti-7333钛合金；ω相；次生α相；等温时效
（State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China）
Abstract:Dilatometry method was used to study the ω phase transformation kinetics of a near-β Ti-7333 titanium alloy Ti-7Mo-3Cr-3Nb-3Al during 350 ℃ isothermal aging for different time. The microstructure evolution was obtained by means of XRD and TEM observation. It is indicated that the single β phase can be obtained during cooling of Ti-7333 alloy from the solution treatment temperature. Aging at low temperature 350 ℃ for 4 h, fine ω particles precipitate in the β matrix homogenously. Aging for 8 h, ω particles grow up with a relatively slow speed and distribute in β matrix evenly and dispersively. After aging for 20 h, the secondly α phase precipitates in the β matrix besides ω particles. And the coarser ω particles form as groups in a quite non-uniform fashion. The morphology of the ω phase particles changes slightly for the formation of secondly α phase. This mainly ascribes that the unstable β phase has no ability to transforms into α phase at low temperature. In order to improve the phase stability, the unstable β phase firstly transforms into ω phase and then the ω phase transforms into α phase.
Key words: Ti-7333 titanium alloy; ω phase; secondly α phase; isothermal aging
