Phase Composition Formation in a V-1469 Alloy (Al–Cu–Li System) during Friction Stir Welding

The morphology of the intermetallic phases and their contents in the welded joint zones of a V‑1469 alloy (Al–Cu–Li system) are studied by X-ray diffraction and transmission electron microscopy. Welding is shown to change the phase composition, the crystallographic texture, and the microhardness of the alloy. According to quantitative X-ray diffraction analysis, the T1-phase content decreases and the δ'-phase content increases in the weld metal. As a result, the microhardness in the weld zone decreases, since the T1 phase is much stronger hardener than the δ' phase. This effect weakens when the weld root is approached.