(中国工程物理研究院 材料研究所，江油 621907)
摘 要: 研究了铸态U-5.5Nb合金连续冷却过程中的组织及相转变行为。利用OM、SEM和XRD对组织特征及相组成进行了分析。结果表明，U-5.5Nb合金在连续冷却过程中发生了不完全的胞状分解，形成了类似于珠光体的片层组织，片层间距为86~186 nm。XRD分析表明片层组织由贫Nb的α相和富Nb的γ1-2中间相组成。胞状分解优先在晶界和夹杂物周围形核并长大。通过对晶界处胞状分解组织特征以及热力学计算分析可以得到U-5.5Nb合金胞状分解满足Fournelle-Clark热激活分解机制。在夹杂物界面上观察到了一层连续的但厚度不均匀的γ1-2相薄膜(30~60 nm)，并且夹杂物和胞状分解聚集体分离。
关键字: U-Nb合金；组织；相转变；胞状分解
（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
