NbCr_2/Nb合金高温蠕变行为

High temperature creep behavior of NbCr_2/Nb alloy

采用机械合金化+热压制备了成分为Nb-22.5at.%Cr的细晶NbCr_2/Nb合金。通过Gleeble 3500型热模拟机上的恒应力压缩试验,研究了合金的高温蠕变行为,并采用透射电子显微镜观察了合金变形前后的组织。结果表明:NbCr_2/Nb合金的稳态蠕变速率随应力的增加和变形温度的升高而加快,1000℃和200 MPa条件下,NbCr_2/Nb合金的稳态蠕变速率为9.0×10-5s-1,1000℃下的应力指数为4.36,而200 MPa下的蠕变激活能为510.7 kJ·mol-1。蠕变变形过程中,Nb基体中位错的滑移、攀移和Laves相NbCr_2中的同步剪切是蠕变变形的主要方式;随着变形温度升高,Nb基体颗粒有形成亚晶的趋势,且两相颗粒界面处应力增大,Laves相NbCr_2颗粒中层错/孪晶密度增加。

The fine-crystal NbCr2/Nb alloy with composition Nb-22.5 at.%Cr was prepared by mechanical alloying and hot pressing.Then,the high temperature creep behaviors of NbCr2/Nb alloy were studied by constant stress compression tests on Gleeble 3500 thermal simulator,and the microstructure of NbCr2/Nb alloy before and after deformation was observed by transmission electron microscopy.The results show that the steady creep rate of NbCr2/Nb alloy increases with the increase of stress and deformation temperature.The steady creep rate of NbCr2/Nb alloy crept at 1000℃,200 MPa is 9.0×10-5 s-1.The stress exponent is 4.36 at 1000℃and the creep activation energy is 510.7 kJ·mol-1 under 200 MPa.The dislocation slip and climb in the Nb matrix and the synchroshear in the Laves phase NbCr2 are the main modes of creep deformation.With the increase of deformation temperature,Nb matrix particle tends to form subgrain,the stress at the interface of two phase particles increases and the density of stacking fault/twinning in the Laves phase NbCr2 particle increases.