Influence of FSP parameters on wear and microstructural characterization of dissimilar TIG welded joints with Si-rich filler metal

Abstract

The welding process is used to join similar or dissimilar alloys, resulting in severe joint softening, uneven grain structure, and inevitable deficiencies. The friction stir process (FSP) can reduce the grain size and enhance the tensile properties. In this work, the FSP was applied to Si-rich TIG welded joints to enhance the tensile properties and microstructure of the TIG-welded joints by variation of rotational tool speed (TRS), and it was observed that the TIG welding defects (solidification defects, micro-voids, porosity, coarse grain structure) were removed, and the grain size of the TIG weldment was decreased. The coarse eutectic Al13Fe4 and Mg2Si phases were transformed into very small phases in the TIG + FSPed joints. The homogenization of the primary α-Al exists in the TIG welded joints was continuously enhanced as the TRS increased. The processed zone with high TRS (1100 rpm) demonstrated higher tensile strength (102.76 MPa), whereas the TIG weldment using filler ER4043 was employed to have an average tensile strength of 72.14 MPa. The ultrafine grain structure of 5.14 μm was found in the TIG + FSPed weldment with a TRS of 1100 rpm, while the coarse grain size of 20.85 μm was found in the TIG weldment.