Microstructural deformation behavior of laser shock peening Ni alloys: Experimental and molecular dynamics simulation investigations

Abstract

Nickel (Ni) alloys are widely used in aerospace and nuclear power applications due to their excellent high-temperature performance, corrosion resistance, and fatigue strength. However, the Ni alloy prolonged exposure to extreme conditions, such as high-temperature vapor and alternating cyclic loads, often faced with challenges such as fatigue failure, corrosion and wear. These issues necessitate post-treatment techniques to enhance surface properties, ensuring the reliability and stability of critical structures and components. This study explores the application of laser shock peening (LSP) for refining the microstructure and improving the mechanical properties of Ni alloy (Inconel 690). Experimental results demonstrate LSP effectively improves surface microstructure (∼400 μm), specially forming fine-grained layer (∼150 μm), increases surface hardness by 21.6 % (from 185(±1.32) HV to 225(±7.57) HV), and introduces a compressive residual stress of −319(±50) MPa. Furthermore, a simulation model was developed using finite element method (FEM) and molecular dynamics (MD) to link microstructure and mechanical properties through strain rate, revealing the formation mechanism of fine grain layers and twin crystal. This work provides a theoretical method for the LSP treatment in Ni alloys, and offers simulation framework for investigating the connection between microstructure and mechanical properties in laser surface engineering technologies.