Reactive insert assisted reduced-current resistance spot welding of 5052 aluminum alloy to pure copper

A reduced-current resistance spot welding technique, which utilizes the heat of reaction from reactive inserts together with the Joule heat, has been applied to join aluminum alloy A5052–H34 sheets to pure copper C1100–O sheets. Employing elemental powder mixtures of Ti–Al and Ti–Mn binary systems as the reactive inserts, well balanced tensile shear load and bonded area are obtained by the latter insert especially in a composition of Ti–75Mn. Since expulsion causes damage to the joint strength strongly, welding conditions are investigated to prevent the strength decrease. Application of a F-type electrode in the aluminum side is effective to avoid the surface expulsion by chilling the melted zone formed through the thickness of the aluminum alloy sheets during welding. As the mating electrode in the copper side, a CF-type one with a tip diameter just larger than that of the melted zone is effective to prevent the inter-layer expulsion by its forging effect. When a welding current of 12 kA is applied for 0.2 s with Ti–75Mn insert and welding force of 1 kN to join aluminum alloy sheets of 1 mm and 2 mm in thickness to copper sheet of 1 mm in thickness, tensile shear loads over 1.5 kN and 1.9 kN are achieved by the use of an electrode pair of CFφ6(Cu)/F(Al), respectively.