热暴露对Nb/NbCr_2合金组织及性能的影响

Effects of Thermal Exposure on Microstructure and Properties of Nb/NbCr_2 Alloy

采用机械合金化+热压工艺制备了成分为Cr-77.5at.%Nb的Nb/NbCr2合金。分别在800,1000,1200℃对其进行10,30,50,100h的真空热暴露实验,研究热暴露对合金组织及性能的影响。结果表明,随着热暴露温度升高和时间延长,Nb/NbCr2合金的相对密度略有增加,1200℃热暴露100h后,合金的相对密度由热暴露前的99.1%增大至99.6%。合金在整个热暴露过程中没有明显的物相变化。合金的维氏硬度随着热暴露时间的延长呈现先升后降的变化趋势;随着热暴露温度升高和时间延长,合金的断裂韧度逐渐下降;合金的室温抗压强度和塑性应变随热暴露时间的延长逐渐增大,屈服强度随热暴露时间延长先增后降。

Nb/NbCr2 alloy with the composition of 77.5at. %Nb was prepared by mechanical alloying and hot pressing. To investigate the effects of thermal exposure on microstructure and properties of Nb/NbCr2 alloy,the samples were exposed to vacuum at 800℃, 1000℃ and 1200℃ for 10h, 30h, 50h and 100 h, respectively. The results show that the relative density of Nb/NbCr2 alloy increases with the thermal exposure temperature raise and time prolonging, varying from 99.1 % to 99.6% after 100 h thermal exposure at 1200℃. No obvious phase transformation can be observed during the whole thermal exposure process. Vickers hardness of Nb/NbCr2 alloy increases firstly and then decreases with the thermal exposure time. Meanwhile, fracture toughness of Nb/NbCr2 alloy decreases with the increase of thermal exposure temperature and thermal exposure time. Compressive strength and plastic strain of Nb/NbCr2 alloy increase gradually with the elapse of thermal exposure time, while the yield strength of Nb/NbCr2 alloy increases firstly and then decreases.