Microstructural characteristics and enhanced mechanical properties of 2024 aluminum alloy resulting from shot-peening treatment

Microstructural characteristics and enhanced mechanical properties of 2024 aluminum alloy associated with shot-peening treatment were investigated by optical microscope (OM), scanning electron microscope (SEM), electron backscatter diffraction technology (EBSD), X-ray diffraction (XRD) and tensile test. The results showed that the shot-peening treatment induces a severe plastic deformation within the surface area of alloys and the depth of the affected area caused by the shot-peening treatment is measured to be 600 +/- 20 mu m. Within the affected area, the formation of twins, curved grain boundaries and the fragmentations of grains were detected. In addition, the microstrain of the shot-peened surface increased to 0.5769% (+/- 0.00215) from 0.2181% (+/- 0.01084) after the shot-peening treatment. Correspondingly, the yield strength, the tensile strength and the uniform elongation were improved to 410.3 MPa (increased by about 11%), 519.4 MPa (increased by about 15.8%) and 19.7% (increased by about 81%), respectively, after the shot-peening treatment. Microstructural characteristics and the variation of microstrain within the affected area mainly account for the enhanced mechanical properties of the shot-peened 2024 aluminum alloys. The results of this work indicate that the shot peening process is one of the effective ways to simultaneously improve the strength and ductility of alloys.