The effect of RFSSW parameters on load capacity of EN AW-6082-T6 aluminum alloy and AlCu bimetallic joints

Abstract This paper presents research into the creation of refill friction stir spot welding (RFSSW) single-lap joints of 6082-T6 aluminum alloy and roll-bonded AlCu bimetallic sheet. The latter sheet comprises aluminum EN AW-1050A and electrolytic copper M1E in Z6 temper condition (after rolling) and with a 1:1 ratio of the Cu:Al layers. The welding parameters involved a variable plunge depth and welding time. The mechanical properties of the joints were determined in tensile/shear tests. The highest average value of the load capacity of the joint was observed in joints made with a tool plunge depth d t = 2.6 mm and total welding time t w = 4 s. The load capacity for this variant was an average of 5986.75 N with standard deviation SD = 166.15 N. A plug-type fracture on the aluminum layer of the bimetallic sheet was observed in RFSSW joints produced with a plunge depth of 2.6 mm. Increasing the tool rotational speed and thus generating heat resulted in a plug-type fracture on the upper sheet (aluminum alloy). In the case of joints produced with a plunge depth of 2 mm equal to the thickness of the upper sheet, the type of fracture mode with both welding times was found to be nugget debonding.