Surface Properties of AA7075 Aluminium Alloy Shot Peened under Different Peening Parameters

Abstract

AA7075 aluminium alloy was shot peened with different size stainless steel shots at different peening pressures while focusing on investigating the surface properties of AA7075 alloy such as surface morphology, topography, and roughness. Since shot peening (SP) is an important mechanical surface treatment which leads to the local plastic deformation in the surface and sub-surface regions and eventually affects surface properties, the present study aims to clarify the effects of SP parameters on the surface properties of AA7075 T6 alloy. A custom-design SP system was used to shot peen the alloy by stainless steel shots with size of 0.1-0.3 mm and 0.4-0.9 mm at peening pressures of 2 bar and 4 bar. The surface properties depending on shot size and peening pressure were investigated by a scanning electron microscope (SEM) equipped with energy dispersive X-Ray spectroscopy (EDX) and a 3D optical profilometer. The surface morphology affected by both parameters; larger shots and higher pressures caused higher plastic deformation, which led to the formation of more complex and rough surfaces in comparison to the surfaces shot peened with smaller shots at lower pressures. 3D surface topographies were visualized the deformation, which revealed the effects of shot size and pressure. The surface roughness increased with increases in both particles size and pressure, which caused highly deformed and rough surface topographies with a great number of dimples. Embedding of fragmented shot particles occurred during peening.