Abstract Four multi-elemental Nb–Si based ultrahigh temperature alloys with nominal compositions of Nb–22Ti–15Si–5Cr–5Mo–4Zr–3Al-2Hf-xV (x = 0, 3, 5 and 10, respectively) (at.%) were prepared by vacuum non-consumable arc-melting. The effects of V addition on the microstructure, room temperature fracture toughness and microhardness, and compressive performance and isothermal oxidation behavior at 1250 °C of the alloys have been investigated. The results reveal that the microstructures of four alloys are all comprised of primary γ(Nb,X)5Si3, Nbss/γ(Nb,X)5Si3 eutectic and Nbss/γ(Nb,X)5Si3/Cr2Nb three-phase eutectic. However, the size, morphology and the amounts of constituent phases obviously vary with increase in V content in the alloys. The microhardness of γ(Nb,X)5Si3 slightly increases with increase in V content in the alloys, while that of Nbss shows an opposite trend due to the solid solution softening effect of V addition. The room temperature fracture toughness is the highest at 3 at.% V addition, and then obviously reduces at higher content of V addition. Both compression strength and oxidation resistance at 1250 °C of the alloys have been degraded by V addition. However, alloying with V obviously improves the adhesion of oxide scale of Nb–Si based ultrahigh temperature alloys.

中文翻译：

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V添加对多元素Nb-Si基超高温合金组织和性能的影响

摘要 四种多元素 Nb-Si 基超高温合金，其标称成分为 Nb-22Ti-15Si-5Cr-5Mo-4Zr-3Al-2Hf-xV（分别为 x = 0、3、5 和 10）（at.% ) 是通过真空非消耗性电弧熔化制备的。研究了V添加对合金显微组织、室温断裂韧性和显微硬度、压缩性能和1250℃等温氧化行为的影响。结果表明，四种合金的显微组织均由初生γ(Nb,X)5Si3、Nbss/γ(Nb,X)5Si3共晶和Nbss/γ(Nb,X)5Si3/Cr2Nb三相共晶组成。然而，随着合金中V含量的增加，组成相的尺寸、形貌和数量明显变化。γ(Nb,X)5Si3 的显微硬度随着合金中 V 含量的增加而略有增加，而 Nbss 由于 V 添加的固溶软化作用而显示出相反的趋势。室温断裂韧性在V添加量为3at.%时最高，随后在V添加量较高时明显降低。合金在 1250°C 时的抗压强度和抗氧化性均因 V 的添加而降低。然而，与 V 合金化明显提高了 Nb-Si 基超高温合金氧化皮的附着力。