Mechanical behavior of Nd:YAG laser welded aluminum alloys

Al alloys, conceived for automotive and aeronautic applications thanks to the high strength/density ratio, exhibit weldability issues common to all light alloys. In particular loss of toughness and soundness of welded joints consequent upon welding operations, possible cracking in the weld metal and metallurgical modifications induced in the heat affected zone. In this paper the weldability of AA2139, AA6110 and AA6156 with the same filler of AA4047 was investigated by comparing features of welds carried out by Nd:Yag laser process. Some samples have been welded of different Al alloys. Welded joints were submitted to optical and SEM metallographic examinations with EDS. Microanalysis measurements were performed to evaluate locally chemical composition and to investigate the nature of the precipitates. Mechanical properties were evaluated through tensile test (T-pull and Hoop stress) and fatigue test (T-pull and Hoop stress). One of the main results is the goodness of this kind of welding between the different alloys for mechanical properties and metallographic features. In particular the configuration AA6156-AA2139-AA4047 is typical for resistance structure in aircraft applications, consisting in extruded AA2139 stringer, responsible to absorbing structural loads and AA6156 skin with high corrosion and crack propagation resistance.