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采用真空非自耗电弧熔炼的方法制备了4种名义成分为Nb-22Ti-16Si-3Cr-3Al-x Hf(x=0,2,4,8,at%)的合金,并于1450℃保温50 h进行了均匀化处理,研究Hf含量对Nb-Si基超高温合金电弧熔炼态及热处理后组织的影响。结果表明:不含Hf的合金的组织主要由初生α(Nb,X)5Si3,Nbss枝晶以及2种共晶(即Nbss/α(Nb,X)5Si3和Nbss/γ(Nb,X)5Si3)构成;加入2 at%Hf,促进了初生γ(Nb,X)5Si3的形成并增加了Nbss/γ(Nb,X)5Si3共晶的含量;当Hf含量增加至4 at%和8 at%时,α(Nb,X)5Si3的形成受到完全抑制,合金中的硅化物仅以γ(Nb,X)5Si3的形式存在。经1450℃/50 h热处理后,原电弧熔炼态的Nbss枝晶与典型的共晶组织形貌基本消失,合金的组织均匀分布。对Hf含量为0 at%和2 at%的合金来说,热处理后的相组成没有发生改变,但α(Nb,X)5Si3的含量减少;而对Hf含量为4 at%和8 at%的合金来说,热处理后Cr2Nb Laves相消失,且在后一种合金中还观察到少量棒状的(Nb,X)3Si相。
Four kinds of alloys with nominal composition Nb-22Ti-16Si-3Cr-3Al-x Hf (x = 0, 2, 4, 8, at%) were prepared by vacuum non- After 50 h incubation, the homogenization treatment was carried out to study the effect of Hf content on the microstructure and the microstructure of the Nb-Si-based superalloy after arc melting and heat treatment. The results show that the microstructure of the alloy without Hf mainly consists of primary α (Nb, X) 5Si3, Nbss dendrites and two eutectics (Nbss / α (Nb, X) 5Si3 and Nbss / γ ). The addition of 2 at% Hf promoted the formation of primary γ (Nb, X) 5Si3 and increased the content of Nbss / γ (Nb, X) 5Si3 eutectics. When Hf content increased to 4 at% and 8 at% , The formation of α (Nb, X) 5Si3 is completely inhibited, and the silicide in the alloy exists only in the form of γ (Nb, X) 5Si3. After heat treatment at 1450 ℃ for 50 h, the Nbss dendrites and the typical eutectic morphology of the original arc melting basically disappeared, and the microstructure of the alloy was uniformly distributed. For alloys with Hf content of 0 at% and 2 at%, the phase composition after heat treatment did not change, but the content of α (Nb, X) 5Si3 decreased. For the alloys with 4 at% and 8 at% In the alloy, the Cr2Nb Laves phase disappeared after heat treatment and a small amount of rod-shaped (Nb, X) 3Si phase was also observed in the latter alloy.