基于碳氮调控的快堆用316型奥氏体不锈钢的辐照损伤机理研究

The austenitic stainless steels used in fast reactors are exposed to high temperature liquid sodium and high neutron fluence. Their microstructural evolution and mechanical properties change will affect the security of reactors during service period. Therefore, the effect of carbon and nitrogen content on microstructure and properties in steels have been widely studied by researchers around the world. This program is proposed to focus on the 316-type austenitic stainless steels with different carbon and nitrogen content. By applying the positron annihilation technique, X-ray diffraction profile line analysis, transmission electron microscopy and nanoindentation, the ion irradiation experiments of thermal-aged and as-received (unaged) alloys are carried out and we will focus on their ion irradiation damage and its interactive mechanisms with long-time thermal-ageing. Firstly, the irradiation defects and properties of as-received alloys will be studied systematically to establish the irradiation damage mechanism due to different carbon and nitrogen content. Then by analyzing the ion irradiation damage of aged alloys, the complex interactive mechanism of the long-time tending towards stable thermal-ageing with irradiation ballistic mixing will be clarified. Finally, the effect of the order of long-time thermal-ageing and irradiation on alloys will be clear by the investigation of long-time thermal-ageing behavior of irradiated alloys. As the above studies are completed, a systematic theory involving carbon/ nitrogen, irradiation resistance and long-time thermal-ageing behavior will be established. It is believed that this program will provide reference for the application of alloys in fast reactors.

快堆用奥氏体不锈钢材料及其部件处于高温钠介质和高剂量的中子环境中，在40年的设计寿期中不可避免地发生微观结构及性能的变化，影响快堆的安全运行。作为奥氏体稳定元素，碳、氮对奥氏体不锈钢微观结构及性能的影响机理成为各国材料工作者的研究热点之一。本项目以不同碳、氮含量的316型奥氏体合金为研究对象，采用离子束辐照时效/未时效状态的合金，利用正电子湮没技术、X射线衍射线型分析技术、透射电镜及纳米力学压痕等设备，揭示合金的辐照损伤机制及其与长时时效的交互作用机制：系统研究未时效材料辐照前后的力学性能及辐照缺变化，阐明辐照损伤机理；研究时效后材料的离子辐照的影响，揭示碳氮长时扩散的热力学稳定与离子辐照的原子混合的竞争机制；研究离子辐照后的时效行为，进一步明确辐照与时效次序不同对材料的影响行为。项目完成后，将建立的辐照条件下的性能——微观结构的关系，可为我国快堆材料的应用提供参考。

快堆用奥氏体不锈钢材料及其部件处于高温钠介质和高剂量的中子环境中，在40年的设计寿期中不可避免地发生微观结构及性能的变化，影响快堆的安全运行。作为奥氏体稳定元素，碳、氮对奥氏体不锈钢微观结构及性能的影响机理成为各国材料工作者的研究热点之一。本项目制备了低碳中氮、中碳中氮及低碳高氮三种类型的316型奥氏体合金，采用离子束辐照时效/未时效状态的合金，主要利用透射电镜对样品厚度进行了测量，采用倒易杆模式对位错环进行了观察，对不均匀的辐照损伤区域的位错环进行了尺寸及数量密度分布研究；采用纳米力学压痕进行了压痕硬度的测量，揭示合金的辐照损伤机制：获得了位错环作为主要硬化源的未时效态合金的硬度随着剂量的变化关系满足n为0.14的幂律关系；碳、氮含量引起的层错能的不同，位错环的尺寸随着层错能的降低而较低，在压痕硬度上则表现出辐照硬化或软化现象；时效会引起辐照硬化行为的改变。本项目所设置的离子辐照参数可与计划入堆辐照参数有一定关联，将来该成果可与中子辐照后检验的组织和性能数据有一定比对，以进一步探讨离子辐照与中子辐照的相关性，具有一定的工程意义。