Laser Beam Welding of 6013 Aluminum Alloy Sheet

Abstract

Butt welds of 1.6 mm thick sheet of the Al-Mg-Si-Cu alloy 6013 were produced using a 3 kW Nd-Yag laser. The sheet was welded in the T4 temper using filler powders of the alloys AL-5%Mg and Al-12%Si. Microstructure, hardness profiles, tensile properties and the corrosion behavior of the welds were investigated in the as-welded condition and after a post-weld heat treatment to the T6 temper. Metallographic sections of the joints revealed a dendritic microstructure exhibiting pores in the fusion zone and a partially melted zone adjacent to the fusion boundary. In the hardness profiles across the weld, minima were observed in the centre of the fusion zone. Strengths of the joints in the as welded T4 condition were 70 and 85 % of the ultimate tensile strength of the base material 6013-T4, using filler alloys Al-5%Mg and Al-12%Si, respectively. Post-weld artificial aging to the T6 temper increased the strengths of the welds made with the filler powders Al-5%Mg and Al-12%Si, approaching 75 and 90 %, respectively, of the ultimate tensile strength of the base material 6013-T6. After immersion in an aqueous chloride/peroxide solution, coupons of welds in the as welded T4 condition were more severely attacked by pitting and intergranular corrosion than the base material 6013-T4, which was found to be susceptible to undermining pitting. When artificially aged to the T6 temper, the welds as well as the parent metal were sensitive to intergranular corrosion, revealing similar depth of corrosion attack.