Microstructure evolution of eutectic Nb–24Ti–15Si–4Cr–2Al–2Hf alloy processed by directional solidification

作     者：Zhen Li Sai-Nan Yuan Li-Na Jia Bin Kong Zhen Hong Hu Zhang 

作者机构：School of Materials Science and Engineering Beihang Universtity Beijing 100191 China 

出 版 物：《Rare Metals》 (稀有金属（英文版）)

年 卷 期：2017年第36卷第6期

页      面：472-477页

核心收录：

学科分类：08[工学] 0806[工学-冶金工程] 0805[工学-材料科学与工程（可授工学、理学学位）] 080502[工学-材料学] 0802[工学-机械工程] 0703[理学-化学] 080201[工学-机械制造及其自动化] 0702[理学-物理学] 

基　　金：financially supported by the National Natural Science Foundation of China (No.51101005) 

主　　题：Nb-Si-based alloy Directional solidification Heat treatment Microstructure evolution Intermetallic 

摘      要：In this work, the near-eutectic Nb-24Ti-15Si-4Cr-2Al-2Hf（at%） alloy was directionally solidified at 1900 ℃ with withdrawal rates of 6, 18, 36, 50 mm·min^-1 and then heat-treated at 1450 ℃ for 12 h. The microstructure evolution was investigated. The results show that the microstructure of the directionally solidified（DS） alloy is composed of Nbss＋Nb5Si3 eutectics within the whole withdrawal rate range, while the variation of rates makes a great difference on the solidification routes,the morphology and size of Nb_（ss）＋Nb_5Si_3 eutectic cells.With the increase in withdrawal rates, the petaloid Nbss＋Nb5Si3 eutectic cells transform into granular morphology. After the heat treatment, a mesh structure Nbssis formed gradually which isolates the Nb5Si3, and the phase boundaries become smoother in order to reduce the interfacial energy. Moreover, two kinds of Nb5Si3 exist in the heat-treated（HT） samples identified by crystal form and element composition, which are supposed as α-Nb5Si3 and γ-Nb5Si3, respectively. This study exhibits significant merits in guiding the optimization of Nb-Si-based alloys＇ mechanical properties.