Assessment of Severe Shot Peening on Surface Characteristics of Al Alloys

Surface grain refinement is a relatively new process aimed to enhance mechanical material properties. In this study Al7075-T6 bars have been shot peened with parameters (shot speed and treatment duration) much stronger from those of conventional shot peening (SP). Residual stress state and microstructure gradient have been observed by means of transmission electron microscopy (TEM), X-ray diffraction (XRD) and nano indentation tester. Formation of a fine grained layer of material on top surface of the specimens was confirmed by TEM and also XRD measurements. XRD results show significant depth affected both in terms of residual stress and full width half maximum (FWHM). Measurements also indicate of notable improvements in cases of hardness and elastic modulus in comparison with untreated material. The results obtained from different peening conditions are then critically discussed and compared. Findings imply that using optimized shot peening parameters, it would be possible to create a fine grained layer on surface of components and consequently increase fatigue life and any other properties affected by grain size.