Experiments and Multiscale Simulation on Enhancement Mechanism of Zirconium Alloy Microstructure and Properties by Laser Shock Peening

Abstract Zirconium alloys are critical materials in nuclear engineering due to their exceptional irradiation resistance and corrosion stability. However, prolonged exposure to extreme operational environments, including a high radiation, mechanical stress, and corrosive media, induces surface degradation mechanisms including stress corrosion cracking and erosion from impurity particle impacts, necessitating advanced surface treatments to improve hardness and corrosion resistance. We explore the application of laser shock peening (LSP) to enhance the surface properties of the Zr4 alloy. Experimental analyses reveal substantial microstructural modifications upon the LSP. The surface grain refinement achieved a maximum reduction of 52.7% in average grain size (from 22.88 to 10.8 μm 2 ), accompanied by an increase of 59% in hardness (204 to 326 HV). Additionally, a compressive residual stress layer (approximately –100 MPa) was generated on the treated surface, which reduces the risk of stress corrosion cracking. To elucidate the mechanistic basis of these improvements, a multiscale computational framework was developed, integrating finite-element models for macroscale stress field evolution and molecular dynamics simulations for nanoscale dislocation dynamics. By incorporating the strain rate as a critical variable, this framework bridges microstructure evolution with macroscopic mechanical enhancements. The simulations not only elucidated the dynamic interplay between shockwave-induced plastic deformation and property improvements but also exhibited a good consistency with experimental residual stress profiles. Notably, we propose the application of strain rate-driven multiscale modeling in LSP research for Zr alloys, providing a predictive method to optimize laser parameters for a tailored surface strengthening. This study not only confirms that LSP is a feasible strategy capable of effectively enhancing the comprehensive surface properties of Zr alloys and extending their service life in nuclear environments, but also provides a reliable simulation methodology in the field of laser surface engineering of alloy materials.