Thermal Degradation Evaluation of HP40Nb Alloy Steel After Long Term Service Using a Nonlinear Ultrasonic Technique
Thermal Degradation Evaluation of HP40Nb Alloy Steel After Long Term Service Using a Nonlinear Ultrasonic Technique
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DOI：
10.1007/s10921-013-0222-8
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发表时间：
2014-01
影响因子：
2.8
通讯作者：
Y. Xiang;M. Deng;F. Xuan
中科院分区：
文献类型：
--
作者：
Y. Xiang;M. Deng;F. Xuan
非线性超声分析已被提出来表征与微观结构演变相关的 HP40Nb 钢的热降解。对热降解损伤的HP40Nb试样进行超声非线性信号测量，结果表明，归一化非线性参数随热加载时间的不同，呈现明显的增加-平台-减少趋势。根据金相研究，实测声学非线性的变化表明，归一化声学非线性由于早期第二相析出物和位错密度的增加而增大，而在长期高温暴露后，由于位错密度的降低、析出物粗化和微孔的萌生，归一化声学非线性降低。此外，还进行了沉淀物-位错相互作用的分析模型计算，以解释微观结构演变与测量的超声非线性之间的相关性。因此，发现超声非线性对 HP40Nb 钢热降解过程中微观结构的演变非常敏感。
Nonlinear ultrasonic analysis has been proposed to characterize the thermal degradation of HP40Nb steel associated with microstructure evolution. Measurements of ultrasonic nonlinear signals were performed in the thermally degraded damaged HP40Nb specimens and the results showed a clear change of increase-plateau-decrease tendency of the normalized nonlinear parameter with respect to the different thermal loading time. Based on metallographic studies, the variation in the measured acoustic nonlinearity reveals that the normalized acoustic nonlinearity increases due to the increases of the second phase precipitates and dislocation density in the early stage and it decreases as a combined result of the reduction of dislocation density, coarsening of precipitates and initiation of micro-voids after long-term high temperature exposure. Moreover, an analytical model calculation of precipitate–dislocation interaction has been performed to interpret the correlation between microstructural evolutions and the measured ultrasonic nonlinearity. Consequently, ultrasonic nonlinearity is found to be strongly sensitive to the microstructure evolutions during thermal degradation of HP40Nb steels.