(中國工程物理研究院 材料研究所，江油 621907)
摘 要: 研究了鑄態(tài)U-5.5Nb合金連續(xù)冷卻過程中的組織及相轉(zhuǎn)變行為。利用OM、SEM和XRD對組織特征及相組成進行了分析。結(jié)果表明，U-5.5Nb合金在連續(xù)冷卻過程中發(fā)生了不完全的胞狀分解，形成了類似于珠光體的片層組織，片層間距為86~186 nm。XRD分析表明片層組織由貧Nb的α相和富Nb的γ1-2中間相組成。胞狀分解優(yōu)先在晶界和夾雜物周圍形核并長大。通過對晶界處胞狀分解組織特征以及熱力學(xué)計算分析可以得到U-5.5Nb合金胞狀分解滿足Fournelle-Clark熱激活分解機制。在夾雜物界面上觀察到了一層連續(xù)的但厚度不均勻的γ1-2相薄膜(30~60 nm)，并且夾雜物和胞狀分解聚集體分離。
關(guān)鍵字: U-Nb合金；組織；相轉(zhuǎn)變；胞狀分解
（Materials Institute, China Academy of Engineering Physics, Jiangyou 621907, China）
Abstract:The microstructures and phase transformation of as-cast U-5.5Nb alloy were investigated during continuous cooling. The results show that the incomplete cellular decomposition happens in the matrix which exhibits a pearlite-like morphology with the interlamellar spacing of about 86-186 nm, and the preferential sites initiate at prior γ grain boundaries and inclusions. The XRD analysis shows that the lamellar microstructure is composed of α phase with depleted Nb element and γ1-2 intermediate phase with rich Nb element. Moreover, The detailed characterization of morphology in grain boundary combining with the calculation indicate that the classical thermally activated motion of the boundary mechanism by Fournelle and Clark can successfully explain the cellular decomposition of the as-cast U-5.5Nb alloy. Some new insights are also found in inclusions interface that a continuous film of γ1-2 phase with a thickness of 30-60 nm and a discontinuity between the inclusion and the cellular decomposition colonies are observed.
Key words: U-Nb alloy; microstructure; phase transformation; cellular decomposition
