【作者】 杨坤山；

【导师】 王铁山；

【作者基本信息】 兰州大学 ， 能源动力（专业学位）， 2025， 硕士

【摘要】 锆合金耐辐照性能优异、耐腐蚀性能良好、力学性能优异,被用作核电站中核燃料包壳材料。在堆内运行的过程中,锆合金包壳会受各种射线及带电粒子的辐照,辐照会改变锆合金的微观结构,使得锆合金性能降低甚至失效。因此,研究辐照后锆合金的微观结构以及相关性能的变化具有重要意义。通常的包壳材料辐照损伤研究一般选择在室温、高温（200-350℃）下进行,本实验采用低温和室温环境研究锆合金的辐照损伤效应,低温环境去除了温度效应（金属的自修复、退火行为等）,更有利于反映材料的本征性质,综合其他高温环境的研究成果,可以使对锆合金辐照损伤效应的研究更加完整、系统化。本论文以商用压水堆中已成熟使用的Zr-4锆合金为研究对象,在低温（-60℃）、室温两种温度环境中进行5 Me V Xe¹⁹⁺辐照实验,利用X射线衍射仪（XRD）、原子力显微镜（AFM）、透射电镜（TEM）以及纳米压痕仪（NI）综合研究Zr-4锆合金的微观结构以及力学性能的变化。主要研究内容及结论如下:（1）Zr-4锆合金主要由hcp结构的α-Zr相组成。合金内部随机分布着Zr（Fe,Cr）₂第二相粒子,尺寸范围为50-200 nm,密排六方结构。（2）Xe离子辐照后,Zr-4锆合金在某些织构发生择优取向,晶胞的晶格常数增大。辐照后的Zr-4锆合金均在（102）、（103）织构发生择优取向,室温辐照下（004）晶面的衍射峰强度明显降低。X射线衍射线性分析表明,辐照后Zr-4锆合金的位错密度增大,没有产生额外的位错环,低温辐照的Zr-4锆合金位错密度与室温辐照的Zr-4锆合金产生的位错环密度没有明显大小区别。（3）Xe离子辐照诱导Zr（Fe,Cr）₂第二相粒子非晶化转变。存在临界非晶化剂量,低温辐照的临界非晶化剂量低于室温辐照的临界非晶化剂量。通过EDS能谱分析,发现Zr（Fe,Cr）₂发生非晶化的机制与Fe元素从第二相粒子扩散进入锆合金基体,Sn元素从锆合金基体扩散进入第二相粒子密切相关。（4）Xe离子辐照Zr-4锆合金的表面均方根粗糙度增大。室温辐照的Zr-4锆合金,表面均方根粗糙度与辐照剂量之间没有明显规律;低温辐照的Zr-4锆合金,表面均方根粗糙度呈现出随辐照剂量增大先增大后减小的趋势。（5）Xe离子辐照后Zr-4锆合金硬度增大,但是杨氏模量不发生明显变化。相同温度下,Zr-4锆合金的硬度随辐照剂量的增加而增大,这是由于辐照剂量的增大在Zr-4锆合金中引入了更多缺陷;辐照剂量相同时,低温辐照的Zr-4锆合金硬度以及增量大于室温辐照的Zr-4锆合金硬度和硬度增量,在本实验的辐照条件下,温度通过影响第二相粒子非晶化行为来进一步影响Zr-4锆合金的硬度及增量。更多还原

【Abstract】 Zirconium（Zr）exhibits excellent radiation resistance,superior corrosion resistance,and outstanding mechanical properties,making it widely used as a nuclear fuel cladding material in nuclear power plants.During in-core operation,zirconium alloy cladding is exposed to high-flux neutrons,various fission fragments,and gamma rays.Irradiation alters the microstructure of zirconium alloys,leading to degraded performance or even failure.Therefore,researching the microstructure and related property changes of zirconium alloys after irradiation is of great significance.Typically,materials irradiation damage studies are conducted at room temperature or high temperatures（200-350°C）.In this experiment,low temperature and room temperature environment are used to study the irradiation damage effect of zirconium alloys,because the low temperature environment removes the temperature effect（self-healing,annealing behavior of metals,etc.）,which is more conducive to reflecting the intrinsic properties of the material.In this paper,the Zr-4 alloy that has been maturely used in commercial pressurized water reactors was used as the research object,and the5 Me V Xe¹⁹⁺irradiation experiment was carried out at low temperature（-60°C）and room temperature.X-ray diffraction（XRD）,atomic force microscopy（AFM）,transmission electron microscopy（TEM）and nanoindentation（NI）were used to study the microstructure and mechanical properties of Zr-4 zirconium alloy.The main contents and conclusions of the study are as follows:（1）Zr-4 zirconium alloy is primarily composed of theα-Zr phase with an hcp structure.The alloy contains randomly distributed second-phase particles at the nanoscale,with sizes ranging from 50 to 200 nm.Through energy-dispersive spectroscopy（EDS）and electron diffraction analysis of the second-phase particles in the Zr-4 alloy matrix,the results indicate that the second-phase particles in the Zr-4zirconium alloy are Zr（Fe,Cr）?phase with a densely packed hexagonal hcp structure.（3）Xe ion irradiation induces an amorphization transformation in Zr（Fe,Cr）?second-phase particles.When the irradiation temperature is room temperature（RT）,the second-phase particles begin to undergo amorphization transformation at an irradiation dose of approximately 1.0 dpa,with a critical dose for complete amorphization being3.0 dpa.However,when the irradiation temperature is low（-60°C）,the second-phase particles are already fully amorphized at an irradiation dose of 1.0 dpa.EDS line scanning and point scanning were performed on the Zr（Fe,Cr）?second-phase particles before and after irradiation.The results show that during the amorphization transformation of Zr（Fe,Cr）?,Fe elements diffuse from the second-phase particles into the zirconium alloy matrix,while Sn elements diffuse from the zirconium alloy matrix into the interiors of the second-phase particles.（4）After Xe ion irradiation,the root mean square（RMS）roughness of the zirconium alloy surface increases.For zirconium alloys irradiated at room temperature（RT）,there is no discernible correlation between RMS roughness and irradiation dose.In contrast,zirconium alloys irradiated at low temperature exhibit a trend where RMS roughness first increases and then decreases with increasing irradiation dose.（5）Xe ion irradiation leads to an increase in the hardness of zirconium alloys.Under the same temperature conditions,the hardness of zirconium alloys increases with the irradiation dose;when the irradiation dose is constant,the hardness of zirconium alloys irradiated at low temperatures is greater than that of those irradiated at room temperature.Through comprehensive analysis,it is concluded that the differing amorphization behaviors of the second-phase particles within the zirconium alloy under the selected irradiation conditions in this experiment are the primary cause of the observed hardness changes.更多还原