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用电磁冷坩埚定向凝固制备了Nb-24Ti-12Si-4Cr-4Al-2Hf(at%)合金。X射线衍射分析(XRD)表明初始生长区和稳态生长区内的物相均为Nbss,β-Nb5Si3和γ-Nb5Si3。通过透射电镜明场像(BFI)和选区电子衍射斑点分析(SADP)确定呈六边形小平面相的硅化物是γ-Nb5Si3,条状或片状形态的硅化物是β-Nb5Si3。扫描电子显微镜照片(BEI)表明:初始生长区和稳态生长区内的组织均由初生的Nbss和Nbss/Nb5Si3共晶组成,其中共晶分为Nbss/β-Nb5Si3和Nbss/γ-Nb5Si3;初始生长区的横截面组织存在2种形态的胞状共晶;稳态生长区的横截面组织存在3种形态的胞状共晶;与初始生长区内的组织相比,稳态生长区内的组织较为细小且分布均匀;γ-Nb5Si3的生长在稳态生长区内受到抑制。
The Nb-24Ti-12Si-4Cr-4Al-2Hf (at%) alloy was prepared by directional solidification using an electromagnetic cold crucible. X-ray diffraction analysis (XRD) showed that both the initial growth zone and the steady-state growth zone are Nbss, β-Nb5Si3 and γ-Nb5Si3. The silicides of the hexagonal faceted phase were confirmed to be γ-Nb5Si3 by the transmission electron microscopy (BFI) and the selected area electron diffraction spot analysis (SADP), and the β-Nb5Si3 silicide was in the form of strip or sheet. The scanning electron micrograph (BEI) showed that the primary growth zone and the steady-state growth zone consisted of nascent Nbss and Nbss / Nb5Si3 eutectics, and the eutectic was divided into Nbss / β-Nb5Si3 and Nbss / γ-Nb5Si3. There were two kinds of cellular eutectic in the cross-section of the initial growth zone. Three kinds of cellular eutectic existed in the cross-section of the steady-state growth zone. Compared with the initial growth zone, the tissue in the steady-state growth zone Relatively small and uniform distribution; γ-Nb5Si3 growth in the steady-state growth zone was inhibited.