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采用液态金属冷却定向凝固技术制备了高铬Nb-Si金属间化合物基复合材料,分析了不同熔化温度和凝固速度下复合材料的相组成及组织特征。结果表明:Nb-22Ti-17Cr-16Si-2Al-2 Hf(原子分数)合金相组成为Nbss、α-Nb5Si3、Laves相NbCr2和少量的(Nbss+Nb5Si3)共晶,定向凝固没有改变复合材料的相组成。熔化温度为1550℃时,Nbss相呈颗粒状,Nb5Si3相呈随机分布的块状或短板条状;随着熔化温度的提高,Nbss转变为枝晶状且沿轴向定向生长,Nb5Si3相转变为有一定定向效果的长板条状。随着凝固速度的增大,组织明显细化且定向效果增强,凝固速度为18 mm/min时,Nb5Si3呈定向效果良好的细长条状。
High-chromium Nb-Si intermetallic compound matrix composites were prepared by liquid metal cooling directional solidification technology. The phase composition and microstructure of the composites were analyzed under different melting temperature and solidification rate. The results show that the phase compositions of Nb-22Ti-17Cr-16Si-2Al-2 Hf alloy are Nbss, α-Nb5Si3, Laves phase NbCr2 and a small amount of (Nbss + Nb5Si3) Phase composition. When the melting temperature is 1550 ℃, Nbss phase is granular, Nb5Si3 phase is randomly distributed in the shape of block or short strip. With the increase of melting temperature, Nbss transforms into dendrite and grows along the axial direction. Nb5Si3 phase transformation For a certain directional effect of the long strip. With the increase of the solidification rate, the microstructure is obviously refined and the directional effect is enhanced. When the solidification rate is 18 mm / min, Nb5Si3 shows an oriented strip with good orientation.