Microstructure evolution of eutectic Nb–24Ti–15Si–4Cr–2Al–2Hf alloy processed by directional solidification
来源期刊：Rare Metals2017年第6期
论文作者：Zhen Li Sai-Nan Yuan Li-Na Jia Bin Kong Zhen Hong Hu Zhang
文章页码：472 - 477
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 Nbss+Nb5Si3 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.
Zhen Li，Sai-Nan Yuan，Li-Na Jia，Bin Kong，Zhen Hong，Hu Zhang
School of Materials Science and Engineering, Beihang Universtity
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 Nbss+Nb5Si3 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.
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