Analysis of Influence of Ultrasonic Shot Peening on Surface Plastic Behavior of Superalloy

This work focuses on the effects of ultrasonic shot peening (USP) on grain refinement and orientation behavior in the surface region of GH4151 superalloy. The microstructure evolution of the alloy under USP durations were studied. The effects of USP-induced grain refinement, orientation, and dislocation motion behavior were analyzed. The results indicated that during the USP process, the plastic deformation of the surface layer of superalloys is accompanied by changes in grain size and orientation. The random impact of the spheres on the surface area promotes grain refinement and grain rotation, enhancing the randomness of grain orientations and reducing the texture strength and the proportion of "soft" orientation distribution. Over a long period of treatment, a large number of spheres cause the slip planes and slip directions of each grain to rotate due to the additional shear stress from the impact, resulting in relatively consistent plastic deformation on the surface and the enhanced randomness of grain orientations, thus reducing the high texture strength introduced by previous machining processes. The understanding of dislocation pile-up behavior and the relationship between externally applied shear stress, pile-up characteristics, and grain refinement is essential for optimizing the USP process and achieving the desired material properties.