Abstract
Many decades ago, aluminum - copper (Al-Cu) 2024 alloy has been widely used in
the wings and barrel sections of aircraft structures due to its high damage tolerance capabilities.
Innovative aluminum - copper - lithium (Al-Cu-Li) alloys such as 2198, have been recently
developed and is supposed to replace aluminum alloy (AA) 2024 in aerospace industry applications.
The current trend of the aerospace industries is to further reduce the airframe structural
weight and respective manufacturing costs as well as to introduce advanced welding methods
as alternative to the classical riveting process for manufacturing of primary aircraft structures.
Laser beam welding (LBW) of fuselage structures from aluminum alloys is already established
in the aircraft industry for lower fuselage panels since the welded panels provide higher
buckling strength and lower weight when compared to the classical riveted designs.
The mechanical behavior of both non-welded and laser beam welded aluminum-lithium
alloy 2198 specimens are examined in the present work. Sheets with nominal thickness of 3.2
mm were laser beam butt welded using two different filler wires, namely AA4047 (Al-Si) and
AA2319 (Al-Cu), of diameters 1.2 mm and 1.0 mm, respectively. The specimens were
machined from the two types of welded sheets, according to the ASTM standards. Some of
the specimens were artificially aged before and post to the welding process at 170 oC and for
different ageing times so as to bring the material in all possible ageing conditions.
The specimens were examined with the aid of light optical microscope to investigate the
morphology formation of the precipitations on the fusion zone and the heat-affected zone for
the different filler materials.
It was shown that the different filler wire plays a critical role on the fracture properties of
the welded joint and especially for the fracture toughness. The Al-Cu filler wire responded
more accurately to the artificial ageing conditions compared to the respective Al-Si filler wire.
