中文摘要：

以Nb-16Si-22Ti-2Al-2Hf成分为基础,分别添加了2%和17%（原子分数,后同）的Cr元素替代Nb（分别称2Cr和17Cr合金）,研究了Cr含量对Nb-16Si-22Ti-2Al-2Hf合金相组成、显微组织形貌、室温断裂韧性和高温强度的影响,分析了高低温失效机制。结果表明,铸态和1375℃×100h热处理后2Cr合金由Nbss和Nb5Si3两相组成;当Cr含量为17%时,出现了具有C15结构的LavesCr2Nb相,合金由Nbss、Nb5Si3和Cr2Nb三相组成,热处理后在Nb5Si3中还析出了球状Cr2Nb相。随着Cr含量由2%提高到17%,热处理合金的室温断裂韧性KQ由14.32MPa.m1/2下降到10.30MPa.m1/2。合金强度与Cr含量的关系受温度影响,随Cr含量提高,室温和1150℃时合金的硬度或强度增高,而1250℃和1350℃时合金强度降低。如1150℃时2Cr和17Cr合金的屈服强度σ0.2分别为349MPa和387MPa;1350℃时分别为306MPa和74MPa。

英文摘要：

Based on the composition of Nb-16Si-22Ti-2Al-2Hf,2 at% and 17 at% Cr （referred to as 2Cr and 17Cr alloys） are respectively added to replace Nb. Effects of Cr additions on phase constitution,microstructure,room temperature fracture toughness and high temperature strength are investigated,and failure mechanisms at room and high temperatures are analyzed. It is found that the microstructure of the as-cast and heat-treated （annealed at 1 375 ℃ for 100 h） 2Cr alloy is composed of Nbss and β-Nb5Si3,while that of the 17Cr alloy consists of the Nbss,β-Nb5Si3 and Laves Cr2Nb with a C15 structure,and the spherical C15-Cr2Nb precipitates are found in the β-Nb5Si3 of the heat-treated 17Cr alloy. As the Cr content increases from 2 at% to 17 at%,room temperature fracture toughness KQ of the annealed alloy decreases from 14.32 MPa·m1/2 to 10.30 MPa·m1/2. Strength,as a function of the Cr content,is dependent on temperature. At room temperature and 1 150 ℃,the hardness or strength increases with the Cr content,whereas at 1 250 ℃ and 1 350 ℃,the strength decreases. For example,the 0.2% yield strengths σ0.2 of the 2Cr and 17Cr alloys are 349 MPa and 387 MPa at 1 150 ℃,but 306 MPa and 74 MPa at 1 350 ℃,respectively.