The Effect of Laser Shock Peening on Dislocation Morphology and Microstructural Evolution of AA5083-H116

Abstract

The AA5083-H116 aluminum alloys (Al-4.7Mg-0.62Mn-0.29Fe-0.15Si-0.099Cr-0.094Zn-0.036Cu-0.018Ti-0.086Other) are lightweight structural materials for marine applications. Due to the high magnesium content (>3wt.%), the sensitization of Al3Mg2 β-phase and susceptibility for intergranular stress corrosion cracking (IGSCC) in AA5083-H116 significantly increases under thermal exposure. The effects of laser-shock peening (LSP) on the kinetics of β-phase were studied via accelerated sensitization heat treatments between 70-175℃ for times between 5-3,600 hours. Optical microscopy, transmission electron microscopy (TEM), and finite element method (FEM) modeling were utilized to study the effect of LSP on AA5083-H116 microstructural evolution, dislocation morphology, and stress-strain distribution. FEM results showed LSP induces plastic compressive deformation near the surface. TEM observations confirmed the models, showing dislocation density increased by a factor of ~4.7, with residual tensile stresses throughout the thickness. The kinetics of β-phase precipitation and coarsening were not impacted by LSP; however, it is recommended that its influence on IGSCC should be investigated further.