Fe对Nb-16Si-22Ti-2Cr-2Al-2Hf合金组织与高温压缩性能影响研究

Effects of Fe on Microstructures and High-Temperature Compressive Mechanical Properties of Nb-16Si-22Ti-2Cr-2Al-2Hf Based Alloy

摘要:

采用真空非自耗电弧炉制备了不同Fe含量的Nb-16Si-22Ti-2Cr-2Al-2Hf-xFe(x=0,1,2,3,原子百分数)四种合金。采用XRD对合金相结构分析表明,制备的合金由Nbss相,Nb₃Si相及Nb₅Si₃相组成。微观组织分析发现,随着Fe元素含量的增加,促进共析反应Nb₃Si→Nbss+Nb₅Si₃的进行,合金相组成由Nbss+Nb₃Si转变为Nbss+Nb₅Si₃。Nb₃Si组织由连续变成分散的块状,体积分数减小,Nbss相由树枝晶状转变为等轴晶状,平均晶粒大小约5μm,体积分数有所增加。采用Gleeble-1500热模拟机对合金进行高温压缩实验,发现随着Fe元素含量的增加,压缩温度的升高及应变速率的降低,合金压缩开裂倾向减小,应力峰值降低,变形能力增加。Fe元素的添加令Nb-Si基超高温合金具有更好的高温塑性变形能力,对改善Nb-Si合金的热加工性能具有重要的意义。

Abstract:

Four kinds of multiphase refractory Nb-16Si-22Ti-2Cr-2Al-2Hf-xFe(x=0,1,2,3)alloys were prepared by vacuum arc melting. XRD analysis reveals that the composites consist of Nb solid solution(Nbss), intermetallics Nb₃Si and Nb₅Si₃ phase. The addition of Fe promotes the eutectic reaction L→Nbss+Nb₅Si₃, which changes the phases of alloy phases from Nbss + Nb₃Si to Nbss + Nb₅Si₃.The volume fraction of ductile phase Nbss increases with increasing of Fe addition, leading to the reduction of compressive strength. Meanwhile, temperature and strain rate also have important influence on compressive strength of the alloys. The addition of Fe element makes Nb-Si based superalloy have better high temperature plastic deformation ability, which is of great significance to improve the hot workability of Nb-Si alloy.