Laser shock processing of materials. Physical processes involved and examples of applications

Abstract

Laser shock processing (LSP) consists in irradiating a metallic target with a short (about 20 ns) and intense (> 1 GW/cm2) laser light with application to generate, through a high pressure surface plasma (> 1 GPa), a plastic deformation and a surface strengthening within materials. This paper first reviews the physical processes involved through an analytical modelling of the generation pressure mechanism in confined plasma regime. Limiting factors like the dielectric breakdown phenomenon in the confining medium are also discussed together with current research trends tending to improve the laser-material coupling like using short rise time pulses instead of gaussian ones or shorter wavelengths than traditional λ = 1.06 μm. Surface mechanical effects are also theoritically and experimentally presented. They consist mainly of compressive residual stress generations to the first 1-2 mm in depth that are the key to enhanced mechanical properties Regarding the field of LSP applications, two potential ones are presented : the fatigue behavior improvement of aluminum alloys and a thermomechanical treatment using both CO2 laser for surface quenching and pulsed Nd-Glass laser for mechanical shock strengthening. As a conclusion, attractive and detrimental features of LSP are discussed with objective to define an industrially convenient laser shock configuration.Laser shock processing (LSP) consists in irradiating a metallic target with a short (about 20 ns) and intense (> 1 GW/cm2) laser light with application to generate, through a high pressure surface plasma (> 1 GPa), a plastic deformation and a surface strengthening within materials. This paper first reviews the physical processes involved through an analytical modelling of the generation pressure mechanism in confined plasma regime. Limiting factors like the dielectric breakdown phenomenon in the confining medium are also discussed together with current research trends tending to improve the laser-material coupling like using short rise time pulses instead of gaussian ones or shorter wavelengths than traditional λ = 1.06 μm. Surface mechanical effects are also theoritically and experimentally presented. They consist mainly of compressive residual stress generations to the first 1-2 mm in depth that are the key to enhanced mechanical properties Regarding the field of LSP applications, two potential ones are...