增材制造316L不锈钢核能材料微纳界面结构辐照效应及抗辐照强化调控研究

Additive manufacturing (AM) provides innovation ideas for the manufacture of nuclear power equipment with complicated structure. However, materials processed by AM technology present special micro/nano-interfacial structures, which differ from those made by any other traditional processing technologies. Effects and mechanisms of the micro/nano-interfacial structure on the radiation damage of materials exposed to the extreme environments inside the nuclear reactors need further study. This work is the frontier in the interdiscipline composed of nuclear technology and materials science. In this project, the main works focus on the radiation-induced segregation and radiation defects self-healing effects of 316L austenitic stainless steel processed by Selective Laser Melting (SLM) technology, to figure out the two key scientific problems - “The influence mechanisms of sub-grain cellular boundaries on the radiation-induced segregation behaviors” and “The influence mechanisms of sub-grain cellular boundaries and nano-amorphous particles on the helium atoms diffusion behaviors synergized by radiation defects”. The main works include the following four parts: (1) To investigate the influence of radiation damage on the microstructure evolution and performance degradation of the 316L stainless steel processed by SLM. (2) To illuminate the radiation-induced segregation behavior and mechanisms of the solute atoms near the sub-grain cellular boundary networks. (3) To reveal the effects and mechanisms of the sub-grain cellular boundary networks and nano-amorphous particles on the helium atoms diffusion behaviors synergized by radiation defects. (4) To adjust the micro/nano-interfacial structure of 316L stainless steel processed by SLM to achieve greater radiation tolerance performance. This project will provide the theory foundation for the radiation effects evaluation and performance strengthening of the AM processed 316L stainless steel for nuclear reactor application.

增材制造技术为解决核电装备复杂构件的制造难题提供了新的思路，但运用该技术成形的材料内部存在有别于传统工艺的微纳界面结构，该结构对材料在核反应堆内极端环境下的辐照损伤性能的影响规律与机制亟待深入研究。开展此研究是核技术与材料学科交叉结合的前沿。本项目以增材制造316L不锈钢为对象，针对材料的辐致元素偏析行为和辐照损伤自修复效应，围绕“纳米胞状亚晶界对辐致元素偏析影响及机制”与“亚晶界、非晶颗粒对辐致缺陷协同氦原子迁移的影响及机制”两个关键科学问题开展研究，以期探究辐照损伤对增材制造316L不锈钢组织结构、宏观性能的影响规律；揭示纳米胞状亚晶界上溶质原子辐致偏析规律与物理机制；阐明纳米胞状亚晶界及纳米非晶颗粒对辐致缺陷协同氦原子扩散的作用效应与机理；实现增材制造316L不锈钢微纳界面结构的抗辐照优化调控。本项目研究工作将为增材制造316L不锈钢作为核能材料的辐照效应评估及性能优化提供理论基础。

增材制造技术为解决核电装备复杂构件的制造难题提供了新的思路，但运用该技术成形的材料内部存在有别于传统工艺的微纳界面结构，该结构对材料在核反应堆内极端环境下的辐照损伤性能的影响规律与机制亟待深入研究。本项目以增材制造316L不锈钢为对象，针对材料的辐致元素偏析行为和辐照损伤自修复效应开展研究。主要研究内容与结论如下：.（1）通过对选区激光熔化（SLM）技术成形316L不锈钢的微观表征研究发现，SLM成形316L不锈钢中分布着大量胞状亚晶界、非晶纳米析出相及高密度位错结构；SLM 316L不锈钢微观组织存在各向异性，其中扫描面晶粒择优取向为<101>，沉积面为<001>。相较于冷轧（CR）316L不锈钢，SLM 316L不锈钢具备更加优异的强度及抗腐蚀性能，但延展性下降。.（2）利用惰性气体He、Xe离子辐照，研究了室温及350 ℃下SLM 与CR 316L不锈钢微观结构、力学性能以及耐腐蚀性能受辐照影响的变化规律。结果表明，与CR 316L不锈钢相比，由于亚晶界提升层错能及细化晶粒的作用，SLM 316L不锈钢具有更加优异的抗辐致相变、硬化性能。由于位错密度以及层错能的差异，室温下SLM 316L不锈钢中出现肿胀早于CR 316L不锈钢；350 ℃ 3.7 dpa辐照，两种钢肿胀率均为1%，肿胀差异不明显；CR 316L不锈钢辐照后均出现腐蚀性能下降现象，而SLM 316L不锈钢仅在350 ℃ 3.7 dpa辐照下抗腐蚀性能退化。.（3）针对激光熔融奥氏体不锈钢中的各种界面结构附近的缺陷演化展开模拟，分析界面构型对辐致缺陷演化、溶质元素辐致偏析的影响。研究发现，在亚晶界附近出现空位形成能谷区，说明亚晶界对于点缺陷具有俘获能力；对于Σ3{111}、Σ9{114}界面，未观察到晶界处的辐致偏析，对于Σ3{112}，界面处可观察到轻微的Ni元素富集，对于Σ13{510}界面，结果发现在晶界处Fe、Cr元素为M型分布，而Ni元素则呈W型偏析。. 本项目研究工作将为增材制造316L不锈钢作为核能材料的辐照效应评估及性能优化提供理论基础。