Age hardening of laser beam welded aluminium alloy 6082 using scandium containing filler metal

Abstract

Sheet materials, of thickness 2 mm, of the aluminium alloy AlSi1MgMn (6082) in the aging conditions T4 and T6 were laser beam welded with a CO₂ laser using two different filler wires: a relative common filler AlSi7Mg and a new developed scandium-containing filler AlMg7Sc. To check the feasibility of a post-thermal treatment, the aging behaviour of the base material AlSi1MgMn in the conditions T4 and T6, as well as the aging behaviours of the fusion zones AlSi1MgMn/AlSi7Mg and AlSi1MgMn/AlMg7Sc were investigated. For the base material AlSi1MgMn-T4 and the fusion zone AlSi1MgMn/AlSi7Mg, close square butt weld, a similar aging behaviour is found at moderate temperatures and durations. So aluminium welds with almost constant hardness profiles along the base material, heat affected zone, and fusion zone can be produced by post-aging the welded joint. For the base material AlSi1MgMn-T4 and the fusion zone AlSi1MgMn/AlMg7Sc, close square butt weld, the aging behaviour is different. At temperatures and durations necessary to form precipitates in the fusion zone, the base material is overaged. This behaviour could be improved for single V butt welds. A strong influence of the welding parameters on the aging behaviour of the fusion zone is found, because the amount of melted base and filler materials as well as the solidification rate determine the chemical composition and microstructure of the fusion zone in the as welded state.