辐照损伤和液态铅协同作用下铁晶界溶解腐蚀和脆化的模拟研究

The accelerator driven system has merits of efficiency, safety and cleanliness, but its structure materials will suffer more severe irradiation damage than that in traditional nuclear systems and dissolution corrosion and embrittlement from liquid metals. Experiments indicate that irradiation can not only aggravate the liquid metal corrosion, but also accelerate the embrittlement to iron-based structural materials. But it is not clear how irradiation damage accelerates liquid metal dissolution corrosion and embrittlement to the structural material. This project would perform the theoretical study on synergistic effect of irradiation damage and liquid metal at grain boundary of iron. Based on α-Fe, by combining molecular dynamics and molecular statics methods, we explore the liquid lead dissolution corrosion and penetration processes at the interaction of non-irradiated grain boundary and solid-liquid surface and the interaction of irradiated grain boundary and solid-liquid surface, respectively. By comparing above two processes, we reveal the synergistic effect of irradiation damage and liquid metal at interaction of grain boundary and solid-liquid interface by examining the segregation of irradiation defects and liquid Pb and the combination of between them. Based on the energetic and dynamic properties of the interaction between irradiation defects and liquid Pb, we investigate the evolution of irradiation defects and liquid Pb in large systems during long time, and evaluate the radiation resistance and liquid metal corrosion resistance of nano-crystalline iron.

加速器驱动的次临界核能系统具有高效、安全、洁净等特点，但其服役的结构材料除了要承受比传统核能系统中更强的辐照损伤，还要承受液态金属的腐蚀。实验表明，辐照损伤会加剧液态金属对铁基结构材料（尤其是马氏体钢）的溶解腐蚀和脆化。但是，辐照损伤促进液态金属对结构材料溶解腐蚀和脆化的微观机制尚不清楚。本项目拟开展“辐照损伤和液态铅协同作用下铁晶界溶解腐蚀和脆化的模拟研究”。以α-Fe为研究对象，应用分子动力学、分子静力学方法，通过对比研究“无损伤的晶界裸露Fe表面”和“辐照损伤的晶界裸露Fe表面” 在液态铅中溶解和渗透过程，考察铁表面和晶界处的辐照缺陷与液态铅的扩散、偏聚和复合行为，揭示辐照损伤与液态铅协同作用下铁晶界溶解腐蚀和脆化机理。基于这些腐蚀过程的能量学和动力学参数，应用实体动力学蒙特卡洛方法考察大体系铁晶界处辐照缺陷和液态铅的长时间协同演化规律，为评估纳米晶铁抗辐照和耐腐蚀性能提供理论依据。

加速器驱动的次临界核能系统具有高效、安全、洁净等特点，但其服役的结构材料除了要承受比传统核能系统中更强的辐照损伤，还要承受液态金属的腐蚀，尤其是辐照损损伤会加剧液态金属对铁基结构材料（尤其是马氏体钢）的溶解腐蚀和脆化，导致材料性能退化失效。因此，本项目以α-Fe为研究对象，结合第一性原理、分子动力学方法和动力学蒙特卡洛方法，通过对比有无辐照情况下铁表面和晶界液态金属溶解和扩散过程，考察铁表面和晶界处的辐照缺陷与液态铅的扩散、偏聚和复合行为，揭示辐照损伤与液态铅协同作用下铁晶界溶解腐蚀和脆化机理。研究表明，液态金属的溶解腐蚀与铁表面结构有关，表面原子第一近邻配位数越大，抗溶解腐蚀能力越强，且腐蚀程度随着服役温度升高而增大。辐照环境下，晶界作为缺陷阱和缺陷扩散通道，吸收大量缺陷，促进缺陷扩散，进而导致液态金属偏聚在晶界附近，加速材料的溶解腐蚀和脆化。基于这些腐蚀过程的能量学和动力学参数，应用实体动力学蒙特卡洛方法考察大体系铁晶界处辐照缺陷和液态铅的长时间协同演化规律。研究表明，随着温度升高和辐照剂量增大，溶解腐蚀严重加剧；随着晶粒尺寸的增大，溶解腐蚀降低。这些研究不仅揭示了辐照缺陷与液态金属原子协同作用的微观机制，还为实验上设计抗腐蚀、好力学性能材料提供理论依据，并为评估铁基结构材料抗辐照、耐腐蚀性能提供思路。