(北京航空材料研究院，北京 100095)
摘 要: 为细化铸造TiAl基合金的显微组织，将成分为Ti-44.9Al和Ti-44.3Al-3.0Cr(摩尔分数， %)的两种合金在略高于Ti-Al共析温度的1150℃进行长时保温处理。结果表明，保温一定时间后， 两种合金中的Ti3Al+TiAl片层组织都会发生不连续粗化转变，这种转变的结果能在一定程度上细化合金的晶粒尺寸，其中Ti-44.3Al-3.0Cr合金的晶粒细化效果更佳。 进一步的研究表明 ， 二 元Ti-44.9Al合金中的片层组织的不连续粗化转变近似符合最大熵增率原理和Livingston的稳态扩散模型，其转变控制因素为晶界扩散控制； 合金元素Cr的加入， 原始片间距的细化及表面预变形都会大大促进这种不连续粗化转变过程。
关键字: TiAl基合金 不连续粗化 晶粒细化 相变
（Institute of Aeronautical Materials, Beijing 100095, P. R. China）
Abstract:In order to obtain fine grain microstructures in as-cast TiAl base alloys, alloys of Ti-44.9Al, Ti-44.3Al-3.0Cr(mole fraction, %)were heat treated at 1150 ℃ for long times. The results show that the Ti3 Al+TiAl lamellae in alloys discontinuously coarsen gradually after heat treatment, and this kind of discontinuous coarsening transformation can refine grain size of alloys, the better result of refining grains was achieved in Ti-44.3Al-3.0Cr alloy. Further study shows that the maximum ratio of entropy production principle and Livingston's steady-state diffusion model can appoximately be used to explain the discontinuous coarsening happening in Ti-44.9Al alloy, the controlling mechanism in this alloy is grain boundary diffusion, the adding of Cr, the decrease of lamellar spacing and pre-strain in surface will accelerate discontinuous coarsening greatly.
Key words: TiAl-based alloy discontinuous coarsening grain refinement phase transformation
