Microstructures and mechanical properties of laser welds of 6061 aluminum alloy sheets pre-coated with lubricating film

Abstract

In order to reveal the laser weldability of Al–Mg–Si alloys pre-coated with lubricating film, microstructure and mechanical properties were investigated in pre-coated 6061-O and -T4 aluminum alloy joints. Two types of laser (CO₂ and YAG) were used for welding. No significant reduction in ultimate tensile strength (UTS) was observed in the pre-coated 6061-O joints regardless of the type of laser. The YAG-laser welds of pre-coated 6061-T4 alloy showed 20% reduction in UTS compared to that of the parent alloy. This amount of reduction was similar to that of the non-coated alloy joints. On the other hand, for the CO₂ laser welds, UTS drop of the pre-coated joints was 50%. This was larger than the 30% reduction of the non-coated alloy joints. The reduction of UTS in the CO₂ laser weld was attributed to a large number of porosity in the weld metal.