Duplex stainless steel is a structural material that is highly used in nuclear power plants, especially in the reactor core components and pipelines. Long-term exposure of duplex stainless steel in a high-temperature working environment will cause thermal aging embrittlement. Material deterioration will affect the long-term reliability of nuclear power plants. In this work, we used two different ultrasonic techniques, namely Laser Ultrasound Technique (LUT) and Non-linear Ultrasonic Technique (NUT) for measuring the material properties. The LUT has unique advantages such of being non-contact, non-destructive, and remotely operable, while NUT has considerable measurement sensitivity to the microstructure changes of materials. Therefore, this research mainly focused on duplex stainless steel after the heat aging treatment. The changes in the material properties of the duplex stainless steel after the heat aging treatment were investigated by ultrasonic testing and traditional material testing methods. The results of this study show that the thermal aging with higher duration, the ferrite phase decomposes into Cr-rich αˊ-phase and Fe-rich α-phase. The hardness of both the austenite iron phase and the ferrite iron phase increase with the increase in heat aging time. The phase velocity of duplex stainless steel increases significantly up to a heat aging of 2400 h, and then the phase velocity decreases significantly. After thermal aging treatment at different times, the non-linear factor did not change significantly due to the hardness changes. The non-linear response caused by the heat aging treatment of duplex stainless steel is minimum.

双相不锈钢是一种在核电站，尤其是反应堆堆芯部件和管道中应用较多的结构材料。双相不锈钢长期暴露在高温工作环境中会引起热老化脆化。材料变质会影响核电站的长期可靠性。在这项工作中，我们使用了两种不同的超声波技术，即激光超声波技术 (LUT) 和非线性超声波技术 (NUT) 来测量材料特性。LUT具有非接触、无损、远程操作等独特优势，而NUT对材料的微观结构变化具有相当大的测量灵敏度。因此，本研究主要针对热时效处理后的双相不锈钢。通过超声检测和传统材料检测方法研究了热时效处理后双相不锈钢材料性能的变化。研究结果表明，随着热时效时间的延长，铁素体相分解为富Crαˊ相和富Feα相。奥氏体铁相和铁素体铁相的硬度随着热时效时间的增加而增加。双相不锈钢的相速度显着增加，直至热时效 2400 h，然后相速度显着降低。经过不同时间的热时效处理后，非线性因素并没有因硬度变化而发生显着变化。双相不锈钢热时效处理引起的非线性响应最小。