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采用真空非自耗电弧熔炼制备添加稀土元素的 Nb‐20Ti‐16Si‐3Al‐3Cr‐2Hf合金纽扣锭，稀土元素为不同含量的Sm ，La ，Tb。对铸态合金进行微观组织分析和室温断裂韧度测试。结果表明：合金主要由（Nb ，Ti）相与 Nb5 Si3相组成，不同部位存在多种微观组织，粗大的两相组织存在宏观聚集现象；纽扣锭中普遍存在规则的共晶晶胞和以N b5 S i3相为核心的板条状晶胞；共晶晶胞中心为Nb5 Si3相和铌固溶体相Nbss组成的层片状组织，外围为粗大的“齿状”两相组织；板条状晶胞的N b5 S i3相核心保留了完整的平直界面和规则的棱角，晶胞外围主要由细小网状的硅化物和粗大的树枝状Nbss相组成。使用多元线性回归分析不同稀土含量与合金室温断裂韧度的关系，不同稀土含量的合金室温断裂韧度值分布在11～15MPa · m1／2之间，多元线性逐步回归分析后得到室温断裂韧度 Kq 与稀土含量（Sm ，La ，Tb）的关系为 Kq＝10．344＋6．896La＋2．993Sm。

Nb‐20Ti‐16Si‐3Al‐3Cr‐2Hf alloy was prepared by non‐consumable electrode arc‐melting , alloyed with different content of rare earth elements La ,Sm and Tb .Microstructures and phase com‐position were analyzed .The results show that (Nb ,Ti) and Nb5Si3 are the main phases .Diverse mi‐crostructures in different position of the ingots and coarse phase concentration are observed ;eutectic grains and lath‐like grains with large Nb5 Si3 phase as the core widely exist in these ingots ;the eutectic grain contains lamellar structure internal and coarse “teeth like” structure external ;the Nb5 Si3 phase in the center of lath‐like grains persists straight interfaces and regular edges ,w hich is surrounded by fine niobium silicide network and coarse dendritic niobium solid solution (Nbss ) phase .Multiple linear regression is used to analyze the relationship of REEs ’ content and room temperature fracture tough‐ness of the alloy ,result indicates that room temperature fracture toughness of these ingots is 11‐15 MPa · m1/2 .The regression equation of REEs’ content (Sm ,La ,Tb) to room temperature fracture toughness Kq is Kq=10 .344+6 .896La+2 .993Sm .