Laser Welding of Dissimilar Aluminium Alloys with Filler Materials

Aluminium alloys have great potential in industrial applications due to their high strength and low weight, specially the AA5xxx and AA6xxx series that have particular applications in the aerospace, military and information technology industries. Laser welding is quite used for joining these materials despite their high reflectivity against laser beam radiation. Nd:YAG lasers are used in pulsed wave mode to overcome a set of difficulties, such as the material absorptivity, its thermal expansion coefficient and thermal conductivity. Autogenous welding of dissimilar aluminium alloys brings additional difficulties due to chemical, thermal and mechanical incompatibility, so the use of a correctly selected filler material improves the compatibility of both alloys being joined. This paper describes the work performed aiming to study laser welding of dissimilar alloys of AA6xxx series and of AA5xxx to AA6xxx series with filler wire. A Nd:YAG laser was used in a pulsed wave mode and a set of filler wires was tested aiming to select the filler presenting better performance. The quality of the welds was evaluated by macro and microstructural analysis. Scanning electron microscopy and hardness measurements were also performed. The results indicate that filler wires with low magnesium and high silicon contents allow for a better weld quality, free of porosity (individual or in clusters). However, the mechanical strength has to be considered in order to assure adequate service performance of the components or structures.