【摘要】 利用正电子湮没技术对材料内部原子尺度缺陷和损伤十分敏感的特点,设计了一种新的正电子无损检测(Non-destructive testing,NDT)装置,并使用单一样品分析了形变及辐照损伤材料的缺陷状态,证实该测量系统的可行性和可靠性。正电子NDT有望真正从原子尺度上给出材料损伤的判据,比常用的宏观或微观损伤判据更灵敏,可方便、快速及高灵敏探测两维缺陷分布。更多还原

【Abstract】 Background:The investigation of the material damage state is very important for industrial application.Most mechanical damage starts with a change in the microstructure of the material.Positron annihilation techniques are very sensitive probes for detecting defects and damage on an atomic scale in materials,which are of great concern in the engineering applications.Additionally they are apparatus of non-destruction,high-sensitivity and easy-use.Purpose:Our goal is to develop a system to exploit new non-destructive testing(NDT) methods using positron annihilation spectroscopy,a powerful tool to detect vacancy-type defects and their chemical environment.Methods:A positron NDT system was designed and constructed by modifying the "sandwich structure" of sample-source-sample in conventional Doppler broadening and positron lifetime spectrometers.Doppler broadening and positron lifetime spectra of a single sample can be measured and analyzed by subtracting the contribution of a reference sample.Results:The feasibility and reliability of positron NDT system have been tested by analyzing nondestructively deformation and damage caused by mechanical treatment or by irradiation of metal alloys.This system can be used for detecting defects and damage in thick or large-size samples,as well as for measuring the two-dimension distribution of defects in portable,sensitive,fast way.Conclusion:Positron NDT measurement shows changes in real atomic-scale defects prior to changes in the mechanical properties,which are detectable by other methods of NDT,such as ultrasonic testing and eddy current testing.This system can be developed for use in both the laboratory and field in the future.更多还原