Experimental investigation of the effects of ball burnishing process parameters on mechanical properties of AA7075-T6 aluminum alloy

Depending on the type and geometry of the cutting tool used in machining production methods, the machine tool, the selected parameters and the environmental conditions, many damages occur in the form of scratches, excessive plastic deformation, surface roughness, residual stress, tearing and micro cracks on the machined surfaces. These damages affect the material's fatigue resistance, abrasion resistance, corrosion resistance and many mechanical properties. Many special methods such as grinding, honing and lapping are used in order to eliminate these problems on the surface of the material. It is also preferred in non-conventional methods such as ball burnishing, deep rolling. Due to the advantages and ease of use of the ball burnishing method, it has become more preferred among surface treatment methods in recent times. In this method, the surface roughness is minimized by small plastic deformations without removing chips from the surfaces with the help of the rolling element pressed against the surface with a certain force. While the surface hardness of the material increases in the process, the surface roughness decreases significantly. In this study, the effects of the process parameters of ball burnishing method (burnishing pressure and number of passes) on AA7075-T6 aluminum alloy in terms of fatigue strength, hardness, surface roughness, residual stress, micro hardness were investigated experimentally. As a result of the experiments, it has been determined that the ball burnishing method improves the surface roughness, and the number of passes among the rolling parameters is statistically more effective on the surface roughness (41%) than the rolling pressure (39.6%). It was observed that the applied force and number of passes increased the microhardness of the material and the microhardness of the material increased by approximately 20 HV depending on the increase in the number of force and passes. It has been observed that the sub-surface residual stress increases in the material with the increase of the burnishing force. It has been determined that the fatigue strength of the material is improved and the fatigue life increases. Keywords: Ball Burnishing, Surface Treatment, Fatigue Strength.