纯镍中弥散纳米碳化物颗粒对高温氦脆及肿胀的抑制机理研究

As the most promising candidate structural material of Molten Salt Reactors (MSRs), the Hastelloy N alloy was faced with the high-temperature helium embrittlement and radiation-induced void swelling, which will affect its service performance. In recent years, it was found that the dispersed oxide particles in ODS steels were capable of acting as stable helium trapping sites, which could capture the helium at its surroundings during irradiation, to avoid not only the embrittlement of grain boundaries, but also the swelling of materials caused by helium bubbles. Due to the advantages found of dispersed nanoparticles, we have chosen to add them to nickel-based alloys so as to study their effectiveness in obstructing helium embrittlement. In the preliminary study, the SiC nanoparticles dispersed nickel based alloys (Ni-SiCNP composites) have been prepared using powder metallurgy method. Experimental characterization and theoretical calculations will be carried out in this project to clarify two main scientific issues as follows: (1) The effect mechanism of SiCNP on absorption efficiency of interstitials by dislocations under high temperature helium implantation; (2) The influence of the interfaces between SiCNP and nickel matrix on grain boundary segregation of helium atoms and also the growth of helium bubbles. Based on the above research results, we will clarify the effectiveness of SiCNP in obstructing helium embrittlement of nickel based alloys and formulate relevant mechanisms. This project will lay a solid foundation for the development of high-temperature radiation-resistant nickel based alloys.

熔盐堆主要候选结构材料Hastelloy N合金面临高温氦脆及肿胀的问题，从而影响其服役性能。近年来研究发现ODS钢中的氧化物弥散颗粒不仅能减小钢中位错对自间隙原子的吸收效率，限制氦泡经由位错偏置驱动机制的生长，同时其与基体的界面能俘获氦原子，阻止氦原子向晶界扩散造成的脆化及因氦泡长大导致的肿胀。基于此，我们采用粉末冶金的方法成功制备出碳化硅颗粒弥散的镍基复合材料，并希望其增强基体的抗高温氦脆及肿胀能力。本项目拟在前期材料制备工作的基础上，从实验分析和理论计算两个方面研究以下两个问题：（1）高温氦离子注入下纳米碳化硅颗粒对位错吸收点缺陷效率的影响机制；（2）纳米碳化硅颗粒与基体界面对氦原子向晶界扩散及氦泡生长等行为的影响。根据以上研究结果，探讨纳米碳化物弥散颗粒在增强纯镍抗高温氦脆及肿胀能力方面所起的作用，阐明相关机理，为耐高温辐照的多元镍基合金材料的研发和制备奠定基础。

Hastelloy N合金是公认的熔盐堆用最优候选合金结构材料，然而该合金面临高温氦脆及肿胀的问题，从而影响其服役性能。采用粉末冶金的方法成功制备出碳化硅颗粒弥散的镍基复合材料，通过氦离子辐照实验以及后续的微观结构表征及力学性能测试，结果表明弥散相与基体界面对点缺陷及氦原子的捕获能有效抑制氦泡的长大，从而优化镍基合金的抗氦脆及肿胀的能力。利于理论模拟研究的结果也证实了这一点。进一步地，考虑到氦原子团聚形成氦泡并长大是镍基材料产生氦致损伤的主要原因，我们还利用原位透射电镜（TEM）表征及同步辐射小角X射线散射（SAXS）等技术对镍基材料中氦泡的长大行为及相关机制进行了研究。发现并提出了氦泡的“形变合并”长大机制，是对已有氦泡演化机制的重要补充。这将帮助我们更合理的评估镍基合金在熔盐堆中的服役性能，同时也将为耐高温辐照的镍基合金材料的研发奠定基础。