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采用氧化钇坩埚真空感应熔炼方法制备了Nb-16Si-22Ti-6Hf和Nb-16Si-22Ti-6Hf-2Cr-2Al合金铸锭,并在1500℃时进行了100 h的热处理。结果表明,铸态和热处理后的合金均由铌基固溶体(NbSS)、Nb3Si、β-Nb5Si3和γ-Nb5Si3组成。冷却速度、合金化元素及热处理均会影响合金的组织。冷却速度较低时,铸锭顶部的组织较粗大;合金化元素Cr和Al可以促进Nb3Si的共析转变,使合金铸锭的组织均匀、细化;热处理则促进Nb3Si→Nb5Si3+NbSS的发生,且Nb3Si的尺寸和体积分数均减小,边界变圆润,NbSS枝晶粗化,共晶组织由片层状变为不规则岛状。
The ingots of Nb-16Si-22Ti-6Hf and Nb-16Si-22Ti-6Hf-2Cr-2Al alloy were prepared by vacuum induction melting method with yttrium crucible and annealed at 1500 ℃ for 100 h. The results show that the as-cast and heat-treated alloys consist of niobium-based solid solution (NbSS), Nb3Si, β-Nb5Si3 and γ-Nb5Si3. Cooling rate, alloying elements and heat treatment will affect the alloy organization. When the cooling rate is low, the microstructure of the ingot is coarse. The alloying elements Cr and Al can promote the eutectoid transformation of Nb3Si and make the microstructure of the alloy ingot uniform and fine. The heat treatment promotes the occurrence of Nb3Si → Nb5Si3 + NbSS, And the size and volume fraction of Nb3Si decrease, the boundary becomes rounded, NbSS dendrites coarsening, and the eutectic structure changes from lamellar to irregular island.