Comparison of TIG welded and friction stir welded Al–4.5Mg–0.26Sc alloy

This paper investigates the comparative microstructural and mechanical characteristics of fusion welds (TIG) and solid-state welds (FSW) of Al–4.5 Mg–0.26 Sc heat-treatable aluminium alloy. Microstructures of base metal and welded zones are analyzed by optical (OM) and transmission electron (TEM) microscopy. Particular emphasis is laid on the evolution of hardening precipitates in welded areas. The corresponding mechanical properties are evaluated through microhardness measurements and uniaxial tensile tests. The effect of a post-weld heat treatment on both microstructure and mechanical properties is further examined. The results suggest that hardening precipitates are comparatively more affected by the TIG than by the FSW process. This results in a substantial reduction of mechanical properties of TIG welds that can be partially recovered through a post-weld heat treatment.