Near Surface Stress Gradients Analysis by Gixrd on Laser Shocked 6056 Aluminium Alloy Samples

Laser shock peening (LSP) can introduce a compressive stress profile for improving the materials’ surface mechanic properties. 6065 Aluminium alloy is introduced recently in the aeronautic components. The surface performances of the components are related directly to the surface activity and surface corrosion properties which are influenced by the near-surface stress gradient. So, the determination of residual stress dues to LSP near the surface layer of 6065 alloy is very important for the surface strengthen and for surface activity. Pseudograzing incidence X-ray diffraction (GIXRD) is a non-destructive method and can be used to evaluate the residual stress gradient below the surface at very shallow depths at micrometer or submicrometer scale according to the studied materials. The experiments were carried out by two GIXRD methods: multi-reflection method using the various crystallographic {hkl} family planes and sinψmethod using the various corrected angles (ψ*, φ*, Ω*) with only one crystallographic family. The purpose of this study is to quantify the stress gradient of 6056 aluminium alloy from surface up to 10 micrometers by these two GIXRD methods, then to compare the obtained results. The tensile residual stresses were found in the near surface area by these two GIXRD methods and their evaluation is quiet similar. To explain this phenomenon, a FEM (finite element method) calculation is carried out and perfectly approaches the laser-induced mechanical effects.