AbstractIntrinsic and extrinsic factors that influence the mechanical properties of as welded weldments in an Al–Cu–Li alloy, 2090, have been investigated. Electron beam (EB) and gas tungsten arc (GTA) welds were produced in 2090–T3 and 2090–T8. The tensile properties of as welded and solutionised and aged weldments at 293 and 77 K are presented. The results show that differences in thermomechanical processing between the base metal and the fusion zone lead to inhomogeneities in the weldment microstructure and, consequently, differences in properties. In the as welded condition, the EB and GTA fusion zones lack the strengthening precipitates present in the base metal. As a result, increased base metal constraint on the as welded fusion zone confines the plastic deformation to within the weld and therefore the measured mechanical properties of the weldment are those of the weld material. After equivalent thermal processing, the properties of the EB and GTA weldments are as good as, or better than, those of the base metal. In the post-weld solutionised and overaged condition, the base metal lacks the volume fraction and homogeneity of strengthening precipitates found in the EB and GT Afusion zones, and as a result failure occurs in the base metal.MST/1405