Microstructure evolution and mechanical properties of Nb–Si based alloy processed by electromagnetic cold crucible directional solidification
Microstructure evolution and mechanical properties of Nb–Si based alloy processed by electromagnetic cold crucible directional solidification
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DOI：
10.1016/j.matdes.2013.10.017
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发表时间：
2014-03
影响因子：
8.4
通讯作者：
Yuncheng Yan;H. Ding;Yongwang Kang;Jinxia Song
中科院分区：
文献类型：
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作者：
Yuncheng Yan;H. Ding;Yongwang Kang;Jinxia Song
本文采用电磁冷坩埚定向凝固技术成功地制备了成分为Nb-22Ti-16Si-3CR-3Al-2Hf(at.%)的样品，并研究了其组织演变和力学性能随拉拔速率的变化规律。所有样品的显微组织均为初生Nbss、Nbss+α-(Nb，Ti)5Si3共晶和Nbss+富钛(Nb，Ti)5Si3共晶。随着拉拔率的增加，组织变得细小，表现为胞状共晶平均直径、共晶Nbss颗粒平均直径和平均相间间距减小。同时，室温断裂韧性先降低后升高，高温拉伸强度逐渐提高。Nbss的体积分数、尺寸和长径比以及Nbss/(Nb，Ti)5Si3界面的数目共同决定了断裂韧性。Nbss/(Nb，Ti)5Si3界面数目越多，有利于阻碍位错的运动，从而导致抗拉强度的提高。
In this paper, the samples with the composition of Nb–22Ti–16Si–3Cr–3Al–2Hf (at.%) have been successfully processed by electromagnetic cold crucible directional solidification, and the microstructure evolution and mechanical properties of the samples were investigated as a function of withdrawal rate. The microstructures of all the samples were composed of primary Nbss, Nbss + α-(Nb, Ti)5Si3eutectic and Nbss + Ti-rich (Nb, Ti)5Si3eutectic. With the increase of withdrawal rate, the microstructure became finer, which could be characterized by the decreased mean diameter of cellular eutectic, mean diameter of eutectic Nbss particles and mean interphase spacing. Meanwhile, the room temperature fracture toughness decreased first, and then increased; the high temperature tensile strength increased gradually. The volume fraction, size and aspect ratio of Nbss and the number of Nbss/(Nb, Ti)5Si3interfaces codetermined the fracture toughness. The more number of Nbss/(Nb, Ti)5Si3interfaces was conducive to impeding the movement of dislocation, which caused the improvement of tensile strength.