强流脉冲电子束诱发纯镍表层纳米结构的形成机制

利用强流脉冲电子束（HCPEB）技术对多晶纯镍进行了表面处理，并采用扫描电镜和透射电镜对强流脉冲电子束诱发的表面及亚表面的微观组织结构进行了分析.实验结果表明，HCPEB辐照后表面熔化，形成了深度约为2 μm的重熔层，快速的凝固使重熔层中形成晶粒尺寸约为80 nm的纳米结构.位于轰击表面下方5—15 μm深度范围内强烈塑性变形引起的位错墙和其内部的亚位错墙结构是该区域的主要结构特征.这些缺陷结构通过互相交割细化晶粒，最终导致尺寸约为10 nm的纳米晶粒的形成. 关键词： 强流脉冲电子束 纳米结构 多晶纯镍 位错墙

Mechanism of surface nanocrystallization in pure nickel induced by high-current pulsed electron beam

High-current pulsed electron beam （HCPEB） technique was applied to irradiate the samples of polycrystalline pure nickel. Microstructures of the irradiated surface and sub-surface were investigated by using scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results show that the surface layer melted, and 2 μm depth remelted layer was formed on the top surface. Superfast solidification of melted layer results in the formation of nano-structure of 80 nm grain size in the remelted layer. In the sub-surface regions, the structures of dislocation walls and sub- dislocation walls in it with band shape were induced by severe plastic deformation, which become the dominant structures 5—15 μm below the irradiated surface. Those defect structures crossing with each other results in grain refinement, and nanocrystal grains about 10 nm in size were produced in the sub-surface layer.