Microstructure, microhardness and residual stress of laser additive manufactured CoCrFeMnNi high-entropy alloy subjected to laser shock peening

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 evoluti...

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Bibliographic Details
Published in:Journal of materials processing technology 2020-11, Vol.285, p.116806, Article 116806
Main Authors: Tong, Zhaopeng, Liu, Huaile, Jiao, Jiafei, Zhou, Wangfan, Yang, Yu, Ren, Xudong
Format: Article
Language:English
Subjects:
Compressive properties
Electron backscatter diffraction
Grain refinement
High entropy alloys
High-entropy alloy
Laser shock peening
Laser shock processing
Lasers
Microhardness
Microstructure
Peening
Performance enhancement
Plastic deformation
Residual stress
Strengthening
Surface layers
Tensile stress
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Summary: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.
ISSN:0924-0136
1873-4774
DOI:10.1016/j.jmatprotec.2020.116806