Effect of Diamond Burnishing on the Properties of FSW Joints of EN AW-2024 Aluminum Alloys

The article presents the results of an analysis of the surface roughness parameters, microhardness, and the stresses of the surface layer ofFSW butt joints subjected to the burnishing process with a diamond tip. This can be useful in selecting the optimal parameters of the burnishing process, ensuring the best properties of the surface layer of the FSW joint. Burnishing force and feed rate influence were analyzed according to the two-factor three-level full factorial statistical completed plan PS/DC 3(2). The tested material was 2024-T3 aluminum alloy sheets with a thickness of 2 mm. The results show that burnishing significantly reduced the surface roughness from Sa = 6.46 mu m to Sa in the range of 0.33 mu m-1.7 mu m. This treatment provides high compressive residual stresses sigma x from -86 to -130 MPa and sigma y from -158 to -242 MPa. Microhardness increased from 84.19% to 174.53% compared to butt joints. Based on the obtained results, multi-criteria optimization was carried out. This optimization allows us to obtain a compromise solution ensuring compressive stresses in the surface layer (sigma(x)=-123 MPa and sigma(y)=-202 MPa) and microhardness HV=362.56 mm/mm(2) with the roughness of the weld surface Sa = 0.28 mu m, Sku = 3.93 and Spc = 35.88 1/mm.