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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。
Based on the composition of Nb-16Si-22Ti-2Al-2Hf, 2% Cr and 17% (atomic fraction, the same) Cr were added instead of Nb (2Cr and 17Cr respectively) 16Si-22Ti-2Al-2Hf alloy phase composition, microstructure, room temperature fracture toughness and high temperature strength of the mechanism of high and low temperature failure. The results show that 2Cr alloy consists of Nbss and Nb5Si3 phases after as-cast and 1375 ℃ × 100h heat treatment. When the content of Cr is 17%, the LavesCr2Nb phase with C15 structure appears. The alloy consists of Nbss, Nb5Si3 and Cr2Nb phases, In the Nb5Si3 after heat treatment also precipitated spherical Cr2Nb phase. With the increase of Cr content from 2% to 17%, the room temperature fracture toughness KQ of the heat-treated alloy decreased from 14.32MPa.m1 / 2 to 10.30MPa.m1 / 2. The relationship between alloy strength and Cr content is affected by temperature. With the increase of Cr content, the hardness or strength of the alloy increases at room temperature and 1150 ℃, while the alloy strength decreases at 1250 ℃ and 1350 ℃. For example, the yield strength σ0.2 of 2Cr and 17Cr alloys at 1150 ℃ are 349MPa and 387MPa, respectively, and they are 306MPa and 74MPa respectively at 1350 ℃.