中文摘要：

采用真空非自耗电弧熔炼的方法制备了Nb-Si基超高温合金,分析了Ti含量对合金组织及相成分的影响规律。结果表明,合金中Ti含量对初生（Nb,X）5Si3的晶型及其尺寸和含量有明显影响。当Ti含量较低时（Oat%~10at%）,初生硅化物为α-（Nb,X）5Si3;与未添加Ti的合金相比,含Ti合金的硅化物含量明显增加;当Ti含量为18at%~20at%时,初生硅化物为α-（Nb,X）5Si3和γ-（Nb,X）5Si3,但α-（Nb,X）5Si3的含量随着合金中Ti含量的增加而减少;当Ti含量为22at%~30at%时,初生硅化物仅为γ-（Nb,X）5Si3。随合金中Ti含量的增加,α-（Nb,X）5Si3的尺寸增大,但γ-（Nb,X）5Si3尺寸基本不变。Ti在Nbss和γ-（Nb,X）5Si3中的含量均随合金中Ti含量的增加而增加,但Ti在α-（Nb,X）5Si3中的含量较低且基本不随合金中Ti含量的增加而变化。

英文摘要：

Nb-Si based ultrahigh temperature alloys were prepared by vacuum non-consumable arc melting and the effects of Ti addition contents on their microstructure and phase composition were investigated.The results show that Ti addition contents could exert an obvious influence on the types,sizes and area fractions of primary（Nb,X）5Si3 in the microstructure.When Ti addition content is relatively low（0at%~10at%）,the primary silicides are α-（Nb,X）5Si3 and its area fraction increases significantly with increase in Ti addition content.When the Ti addition content is ranged from 18at%~20at%,the primary silicides are of two types：α-（Nb,X）5Si3 and γ-（Nb,X）5Si3.However,the amount of α-（Nb,X）5Si3 decreases with increase in the Ti addition content in the alloy.When Ti addition content in the alloy varies from 22at%~30at%,there is only one form of primary silicides i.e.,γ-（Nb,X）5Si3.Moreover,as the Ti addition content in the alloy increases,the size of α-（Nb,X）5Si3 increases while the size of γ-（Nb,X）5Si3 is less affected.In addition,as the Ti addition content in the alloy increases,Ti concentration in both Nbss and γ-（Nb,X）5Si3 increases while that in α-（Nb,X）5Si3 is lower and does not change obviously.