(北京航空材料研究院，北京 100095)
摘 要: 為細(xì)化鑄造TiAl基合金的顯微組織，將成分為Ti-44.9Al和Ti-44.3Al-3.0Cr(摩爾分?jǐn)?shù)， %)的兩種合金在略高于Ti-Al共析溫度的1150℃進(jìn)行長時保溫處理。結(jié)果表明，保溫一定時間后， 兩種合金中的Ti3Al+TiAl片層組織都會發(fā)生不連續(xù)粗化轉(zhuǎn)變，這種轉(zhuǎn)變的結(jié)果能在一定程度上細(xì)化合金的晶粒尺寸，其中Ti-44.3Al-3.0Cr合金的晶粒細(xì)化效果更佳。 進(jìn)一步的研究表明 ， 二 元Ti-44.9Al合金中的片層組織的不連續(xù)粗化轉(zhuǎn)變近似符合最大熵增率原理和Livingston的穩(wěn)態(tài)擴(kuò)散模型，其轉(zhuǎn)變控制因素為晶界擴(kuò)散控制； 合金元素Cr的加入， 原始片間距的細(xì)化及表面預(yù)變形都會大大促進(jìn)這種不連續(xù)粗化轉(zhuǎn)變過程。
關(guān)鍵字: TiAl基合金 不連續(xù)粗化 晶粒細(xì)化 相變
（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
