The effect of surface rolling process on mechanical properties of AlZn5.5MgCu Al alloy

Surface rolling processes were applied to AlZn5.5MgCu Aluminum alloy at different penetration depths, different feed rates and different rotational speeds. Surface rolling processes were carried out with a CNC vertical machining center bench using an apparatus with a steel ball tip. The roughness values of the rolling traces formed on the plates after the surface rolling process using different parameters were measured as Ra, which is known as the y-axis arithmetic mean. In order to determine the effect of surface rolling processes on fatigue strength, bending fatigue test specimens were prepared according to DIN 50142 and fatigue tests were carried out. Microhardness measurements of the samples were made with HV0.5 and 40X magnification. Standard metallographic examination preparations of the samples were carried out and microstructure examinations were carried out using optical microscope and scanning electron microscope. It was observed that the surface roughness changed significantly with the surface rolling process. The surface roughness increased with increasing feed rate. Although the feed rate and rotation speed were kept constant, the increase in the immersion depth negatively affected the surface roughness. The base material gave the lowest fatigue life data for the applied stress values. An increase in the fatigue life was observed in the materials to which the surface rolling process was applied. After the surface rolling process, the hardness values of all samples were higher than the hardness value of the main material. EDS analysis results showed the presence of alloy particles containing Al-Mg-Cu-Zn in different wt% amounts in the microstructure. With the surface rolling process, the area affected by rolling was determined in the microstructure at a distance of approximately 94 µm from the surface. It has been determined that the microstructure of the surface-rolled region and the base material region consists of columnar and oriented grains in the rolling direction. However, it was determined that the aspect ratio of the grains applied YH process differed.