WELDING OF LIGHTWEIGHT ALUMINUM-LITHIUM ALLOYS

Lithium-containing aluminum alloys have generated much interest in the aerospace industry because lithium additions to aluminum can decrease the density and improve the stiffness compared to conventional aluminum alloys of comparable strength. In this paper, published studies of the structure and properties of welded aluminum-lithium alloys are discussed. The weldability characteristics of these lightweight alloys using gas metal arc, gas tungsten arc, electron beam and laser beams are summarized. While the alloys appear to be easily fusion weldable, they may be prone to problems of weld porosity, cracking, poor penetration and low joint efficiency. The effects of heat treatment on postweld joint efficiency are also highlighted. Intrinsic problems associated with conventional welding were partially eliminated through laser beam welding. The laser beam weld studies revealed a low degree of surface degradation, an absence of porosity and attractive joint efficiency. The results delineated in the published literature suggest that future studies must concentrate on a more comprehensive and systematic approach to an evaluation of properties if the use of welded aluminum-lithium structures is to be rapidly accepted in numerous industrial applications.