Experimental investigation of shot peening effect on grain size

Shot peening is a type of mechanical surface treatment and applied to enhance mechanical properties against fatigue and stress corrosion cracking failures. Shot peening process can be applied both cold or warm. Shot peening process enhances not only hardness but also strength of materials. This process expose material surface and just below the surface, compressive residual stress. This study, covers formation of ultrafined grain structure of metal surfaces or just below and alteration of mechanical properties due to severe plastic deformation with extra ordinary shot peening conditions. For AISI 1017 mild steel and commercially pure titanium hardness values were measured by nanoindentation tests and observed to be greatly increased from cross-section to surface. Furthermore, existence of ultrafined grain structures on surface and just below the surface is proved with optical and SEM (Scanning Electron Microscope) images.