Activated TIG Friction stir welding Al-Mg-Sc alloy Microstructure Mechanical properties a b s t r a c t 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.

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. Optimizing the design of silica coating for productivity gains during the TIG welding of a 304L stainless steel. Materials and Design, Elsevier, 2007, 28 (9) The performance of silica coatings on TIG (or GTA) welding of AISI304L stainless steel has been studied by investigating the effect of coating geometry and thickness on weld penetrations. Two coating designs are studied. One involves a 20 mm wide continuous coating across the weld zone and the second design formulates two parallel coatings 1-7 mm apart around the joint. The optimum thickness for continuous coatings is limited to about 50 lm whereas for 2 mm apart coatings, the optimum range extends from 70 to 200 lm. The presence of a narrow bare zone in the coating is suggested to be more practical for manual silica application. Tensile tests have been performed to identify the mechanical behavior in different characteristic zones of the welded specimens. The reduced tensile strength of the weld metal is attributed to the flux silica particles.