Effect of Shot Peening Coverage on the Surface Integrity of a 7b50-T7751 Aluminum Alloy

The 7B50 high-strength aluminum alloy was used to investigate the influence of different coverage rates on the fatigue performance of the target. The surface integrity of the shot-peened alloy was characterized using a scanning electron microscope, a surface roughness testing and analysis system, a residual stress analyzer, an X-ray diffractometer, and a micro-hardness tester to examine the correlation between different shot peening parameters and the surface properties, as well as the sub-surface layer. Moreover, the effect of shot peening coverage on the surface morphology, surface roughness, residual stress, and micro-hardness was investigated. After shot peening, the surface roughness of the alloy changed. With an increase in shot peening coverage, the surface roughness of the specimens initially decreased and then increased. When the coverage increased from 100% to 300%, the surface roughness fluctuated slightly but exhibited an overall decreasing trend. The surface became smoother, while the maximum residual stress value gradually increased. The coverage increase had no significant effect on the depth of microhardness, which only slightly increased at higher energy impacts. However, excessively high coverage reduced the value of residual compressive stress on the specimen surface and increased surface roughness. Therefore, considering the three factors of surface roughness, microhardness, and residual stress, the best results for surface peening of this alloy were achieved by maintaining the coverage at 300% with a peening intensity of 0.1–0.2 mmA. Under the optimized conditions, this alloy exhibits good overall surface integrity, demonstrating better shot peening results that align closely with the material properties.