The Effect of RFSSW Parameters on Load Capacity of EN AW-6082-T6 Aluminium Alloy and AlCu Bimetallic Joints

Abstract

In this paper an investigation has been carried out into the creation of Refill Friction Stir Spot Welding (RFSSW) single-lap joints of 6082-T6 aluminium alloy and roll-bonded AlCu bimetallic sheet. The latter sheet comprises aluminium 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 dt = 2.6 mm and total welding time tw = 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 aluminium 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 the heat generated, resulted in a plug type fracture on the upper sheet (aluminium alloy). In the case of joints produced with a plunge depth of 2 mm equal to the thickness of upper sheet, the type of fracture mode with both welding times was found to be nugget debonding.