Abstract Laser shock peening (LSP) is a surface modification technology to synthesize nanostructures on the surface layer of materials, thereby improving mechanical performances. In this work, a laser additive manufactured CoCrFeMnNi high-entropy alloy (HEA) is processed using LSP. The microstructure evolution during LSP is investigated via electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) observations. The micro-hardness distributions on cross-sections and subsurface residual stress states as functions of the laser energy are also determined. Results indicate that the LSP results in a thick hardened layer with high microhardness, and transforming the tensile stress in the subsurface into compressive stress. The microstructure apparently refines because of the formation of nanoscale grains on the surface after LSP. A novel grain refinement mechanism under ultra-high plastic strain is proposed. Surface strengthening modes are proposed to describe the relationship between strengthening behaviors and microstructure characteristics, thereby revealing the strengthening mechanism.

中文翻译：

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激光增材制造CoCrFeMnNi高熵合金激光冲击强化的组织、显微硬度和残余应力

摘要 激光冲击强化（LSP）是一种表面改性技术，用于在材料表层合成纳米结构，从而提高机械性能。在这项工作中，激光增材制造的 CoCrFeMnNi 高熵合金 (HEA) 是使用 LSP 加工的。通过电子背散射衍射 (EBSD) 和透射电子显微镜 (TEM) 观察研究 LSP 过程中的微观结构演变。还确定了作为激光能量函数的横截面的显微硬度分布和次表面残余应力状态。结果表明，LSP 形成了具有高显微硬度的厚硬化层，并将次表面的拉应力转化为压应力。由于 LSP 后在表面形成纳米级晶粒，微观结构明显细化。提出了一种超高塑性应变下的新型晶粒细化机制。提出了表面强化模式来描述强化行为与微观结构特征之间的关系，从而揭示强化机制。