Progressive developments, challenges and future trends in laser shock peening of metallic materials and alloys: A comprehensive review

Grain refinement and arrangement is an effective strategy to enhance tensile and fatigue properties of key metallic components. Laser shock peening (LSP) is one of surface severe plastic deformation methods in extreme conditions, with four distinctive features, namely, high pressure (1 GPa-1 TPa), high energy (more than 1 GW), ultra-fast (no more than nanosecond scale), and ultra-high strain rate (more than 10(6) s(-1)), and generates a deeper compressive residual stress (CRS) field and the formation of a gradient nanostructure in the surface layer to prevent the crack initiation of metallic materials and alloys, which is widely used in aerospace, overload vehicle, ocean engineering, and nuclear power. Despite some investigations of LSP on surface integrity, microstructural evolution, and mechanical properties of metallic materials and alloys, there is a lack of a comprehensive perspective of LSP-induced microstructural evolution, mechanical properties for metallic materials and alloys in the last two decades. Furthermore, the relationship between the mechanical properties of metallic materials and alloys and the LSP processing parameters is presented. In particular, LSP-induced featured microstructure and grain refinement mechanisms in three kinds of crystal structures, for instance, face-centred cubic, body-centred cubic, and hexagonal close-packed metals, are present and summarised for the first time. In addition, some new emerging hybrid LSP technologies and typical industrial applications as important chapters are shown. Finally, the faced challenges and future trends in the next 10-20 years are listed and discussed. Results to date indicate that LSP, as an emerging and novel surface modification technology, has been increasingly used to surface layer of metallic components. These topics discussed could provide some important insights on researchers and engineers in the fields of surface modification and advanced laser manufacturing.

Automated summary

Grain refinement and arrangement is an effective strategy to enhance the properties of metallic components, and laser shock peening (LSP) is a promising surface deformation method. However, there is a lack of comprehensive understanding of the microstructural evolution and mechanical properties induced by LSP in the past two decades. This study summarizes the unique microstructural features and grain refinement mechanisms induced by LSP in three crystal structures, and introduces emerging hybrid LSP technologies and their industrial applications. The challenges and future trends are also discussed.