Jiang Li, Yinling Wang, Hu Rui, Liu Renduo, Ye Xiang-Xi, Li Zhijun, Zhou Xingtai
Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, 201800, P.R. China.
College of Mechanical and Energy Engineering, Huanghuai University, Zhumadian, 463000, P.R. China.
Sci Rep. 2018 May 25;8(1):8158. doi: 10.1038/s41598-018-26426-0.
GH3535 alloy is one of the most promising structural materials for molten salt reactors (MSRs). Its microstructure is characterized by equiaxed grains and coarser primary MC carbide strings. In this study, stable nano-sized MC carbides were obtained in GH3535 alloy by the removal of Si and thermal exposure at 650 °C. Nano-sized MC carbide particles precipitate preferentially at grain boundaries during the initial stage of thermal exposure and then spread all over the grain interior in two forms, namely, arrays along the {1 1 1} planes and randomly distributed particles. The precipitate-free zones (PFZs) and the precipitate-enriched zones (PEZs) of the MC carbides were found to coexist in the vicinity of the grain boundaries. All MC carbides possess one certain orientation relationship (OR) with the matrix. Based on microstructural characterizations, the formation process of MC carbides with different morphologies was discussed. The results suggested that the more-stable morphology and OR of MC carbides in the Si-free alloy provide higher hardness and better post-irradiation properties, as reported previously. Our results indicate the preferential application of Si-free GH3535 alloy for the low-temperature components in MSRs.
GH3535合金是熔盐反应堆（MSR）中最具前景的结构材料之一。其微观结构的特征是等轴晶粒和较粗大的初生MC碳化物串。在本研究中，通过去除硅并在650℃下进行热暴露，在GH3535合金中获得了稳定的纳米级MC碳化物。纳米级MC碳化物颗粒在热暴露初期优先在晶界处析出，然后以两种形式遍布晶粒内部，即沿{1 1 1}面的阵列和随机分布的颗粒。发现MC碳化物的无析出区（PFZ）和富析出区（PEZ）在晶界附近共存。所有MC碳化物与基体都具有一定的取向关系（OR）。基于微观结构表征，讨论了不同形态MC碳化物的形成过程。结果表明，如先前报道的那样，无硅合金中MC碳化物更稳定的形态和OR提供了更高的硬度和更好的辐照后性能。我们的结果表明无硅GH3535合金优先应用于MSR中的低温部件。
