熔盐堆用Hastelloy N合金的氦致辐照损伤行为及机制研究

镍基Hastelloy N合金以优异的抗熔盐腐蚀性能被公认为是最优的熔盐堆用合金结构材料。然而，由于镍易与中子发生嬗变反应产生氦，使得该合金在熔盐堆中服役面临着严重地氦致损伤问题。一方面，氦原子易于在晶界处大量聚集形成氦泡并逐渐长大，降低合金晶界间的结合力，造成材料的脆化；另一方面，晶内的氦泡与合金中的辐照离位缺陷会协同加深合金性能的劣化，从而危害熔盐堆的安全。. 本项目拟在前期工作的基础上，结合实验分析和理论/模型计算两方面的工作，对以下三个主要问题进行研究：（1）Hastelloy N合金晶界处氦泡的长大所需的临界温度（能量）区间；（2）Hastelloy N合金晶界处氦泡的主要长大机制及其与温度的关系；（3）离位损伤和氦泡在Hastelloy N合金微结构演变及性能劣化中可能存在的协同效应。通过本研究工作的开展，可为更合理的评估该合金服役性能提供依据以保障熔盐堆安全。

The Ni-based Hastelloy N alloy was considered as the priority of metal structural materials in Molten Salt Reactors (MSRs) due to its outstanding corrosion resistance to molten salts. However, this alloy can be easily reacted with neutrons to produce helium, which makes the alloy facing serious helium damage when used in MSRs. On one hand, the helium atoms are easy to gather in the grain boundary to form helium bubbles and grow up gradually, reducing the bonding force between the grain boundaries of the alloy and causing the embrittlement. On the other hand, the synergistic effects of helium bubbles and displacement damage may enhance the degradation rate of the Hastelloy N alloy, endangering thus the safe operation of MSRs.. In the preliminary study, the intergranular helium bubbles coarsening in pure nickel and the irradiation damage of the Hastelloy N alloy after single ion beam irradiation have been investigated. Experimental characterization and theoretical / model calculations will be carried out in this project to clarify three main scientific issues as follows: (1) Critical temperature (energy) interval required for the growth of intergranular helium bubbles in the Hastelloy N alloy; (2) The dominant coarsening mechanism of the intergranular helium bubbles in the Hastelloy N alloy and its relationship with the temperature; (3) Synergistic effects of helium bubbles and displacement damage on both the microstructural evolution and also the performance degradation of the Hastelloy N alloy. Based on the above research results, the service performance of the Hastelloy N alloy can be reasonably evaluated to ensure the safety of MSRs.