Lithium bearing aluminium alloys constitute a. relatively new generation of
high performance, lightweight aviation alloys that are being considered fo
r a variety of applications requiring welded construction. As with other al
uminium alloys, there are a number of weldability issues associated with th
ese alloys, including resistance to defect formation during fabrication, me
chanical property degradation, and service performance. This report reviews
the pertinent literature regarding the welding characteristics, properties
, and weldability of a number of commercial alloys. The review is divided i
nto the following major sections: (1) development and physical metallurgy o
f AI-LI-X alloys, (2) microstructure evolution, (3) mechanical properties,
(4) weld cracking susceptibility, (5) porosity formation and prevention, an
d (6) corrosion behaviour. The commercial AI-LI-X alloys are welded using a
variety of processes, including are welding, high energy density welding,
and solid state welding. The strength of welds in these alloys varies widel
y, depending on the welding process, filler metal selection, and post-weld
heat treatment. In general, these alloys have low joint efficiency (ratio o
f weld strength to base metal strength) in the as welded condition and requ
ire post-weld aging to achieve efficiencies substantially above 50%. Weld p
orosity has been a particular problem with these alloys in part due to the
hygroscopic nature of Li-containing aluminium oxides. This problem can be c
ontrolled if proper surface preparation and cleaning procedures are used. T
he AI-Li-X alloys tend to be more susceptible to weld solidification cracki
ng than comparable alloys without Li additions. Basic weld solidification t
heory is used to explain this increase in susceptibility. Some of these all
oys exhibit an unusual fusion boundary cracking phenomenon that is associat
ed with an equiaxed grain zone that forms via a solidification mechanism in
alloys containing Li and Zr.