Abstract
One of the main interests of aircraft industries is to reduce the structural weight of the airframe;
this resulted in the development of innovative, lightweight and high-strength 3rd generation Al-Cu-Li
alloys. Aluminum alloy AA2198 is a new generation of Al-Cu-Li-alloy that has been developed for
fuselage and skin applications in aircraft structures. Among others, laser beam welding (LBW) of
AA2198 is a very promising method for joining aircraft materials and structures. Laser beam welded
joints are already been exploited in airframe structures, as they provide higher buckling strength and
essential lower weight by replacing the respective riveted differential structures.
The effect of laser beam welding process parameters on porosity formation and solidification on
cracking for high thickness AA2198 sheets is examined in the present work. Welding process
parameters like laser power, welding speed and the resulted linear heat input play a pivotal role in the
quality of laser beam welded joints. Therefore, the main objective of the present work is to identify
the appropriate process parameters to produce autogenously (without filler wire) welded joints of
high quality in absence of cracks and pores. The effect of the welding parameters on the
microstructure of the weld was investigated using light optical and scanning electron microscopy.
The results showed that full penetration was not achieved for heat inputs less than 50 J/mm. Advanced
characterization of geometry of the fusion zone shape (V-shape or rectangular) was performed. It was
found that the V-shape fusion welds present lower tensile strength values. To this end, the
investigation was focused on the welds with a geometrical factor close to the rectangular shape and
the existence of other geometrical defects like underfill. The mechanical behavior of optimal buttwelded
joint configurations were investigated by hardness measurements and tensile tests.
