强流脉冲电子束作用下金属锆的微观结构与应力状态

利用强流脉冲电子束 (HCPEB) 技术对金属纯锆进行表面处理, 采用X射线衍射, 扫描电子显微镜及透射电子显微镜详细分析了辐照诱发的表层微观结构和缺陷. X射线分析结果表明, HCPEB辐照后在材料表层诱发幅值为GPa量级的压应力, 并形成{0002}, {1012}, {1120}及{1013}织构. 表层微观结构观察表明, 与其他金属材料不同, HCPEB辐照在材料表层诱发的熔坑数量极少, 多次轰击甚至几乎没有表面熔坑的形成. 此外, 在快速的加热和冷却状态下, 在表面熔化层形成大量的超细晶粒结构, 同时诱发马氏体相变和强烈的塑性变形. 1次HCPEB辐照后表层内形成的变形微结构以位错为主, 孪晶数量较少; 5 次辐照样品的位错密度迅速增高, 孪晶数量也显著增加; 10次辐照后样品中的变形微结构以变形孪晶为主, 且出现二次孪晶现象. 表层晶粒内部变形的晶体学特征不仅决定了表层的织构演化行为, 而且还起到细化晶粒的作用, 为纯锆及锆合金表面强化提供了一条有效的途径. 关键词： 强流脉冲电子束 纯锆 微观结构 应力状态

Surface microstructure and stress characteristics in pure zirconium after high current pulsed electron beam irradiation

High-current pulsed electron beam (HCPEB) technique was applied to irradiate the samples of pure zirconium. The microstructures and defects of the irradiated surface are investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD results show that the high value of stress (GPa order) is introduced within the irradiated surface layer, while the formation of {0002}, {1012}, {1120} and {1013} textures are present after HCPEB irradiation. Microstructure observations demonstrate that the surface craters are rarer, and almost no craters are present after multiple pulses HCPEB irradiation, which is evidently different from the case of other metal materials irradiated by HCPEB. Moreover, a large number of ultrafine grains are formed on the irradiated surface. Martensitic transformation occurs and severe plastic deformation is also induced due to the superfast melting and cooling processes. After one- pulse irradiation, the dislocations are the dominant defects, while the amount of twins is less. After five pulses, the dislocation density and the number of deformation twins increase evidently, whereas dense deformation twins are the central microstructures after ten-pulse irradiation, coupled with the appearance of secondary twins occasionally. The formation of these deformed structures results in a significant effect both on the evolution of surface textures and on grain refinement. It is suggested that HCPEB technique provides an impactful approach for hardening of zirconium and zirconium alloys.
Keywords： high current pulsed electron beam pure zirconium microstructure stress characteristic