Investigation of microstructure and mechanical characteristic of underwater friction stir welding for Aluminum 6061 alloy – Silicon carbide (SiC) metal matrix composite

Abstract

Demand for metal matrix composites (MMCs) is expected to increase in these applications, such as in the aerospace and automotive sectors. Adequate joining techniques, which are important for structural materials, have not yet been developed for Metal Matrix Composite (MMCs), however. This work aimed to demonstrate the feasibility of friction stirwelding (FSW) and underwater friction stir welding (UFSW) for joining Al 6061/5, Al 6061/10, and Al 6061/18 wt. %SiCcomposites have been produced by utilizing reinforce stir casting technique. Two rotational speeds,1000and 1800 rpm, and traverse speed 10mm \min were examined. Specimen composite plates 10 mm thick have been successfully welded by FSW. For FSW and UFSW, a tool made of high-speed steel (HSS) with a conical pin shape was used. The result revealed that the ultimate tensile strength ofthe welded joint by FSW and UFSW at rotation speed 1800 rpm for (Al 6061/18 wt. % SiCcomposites) was 195 MPa and 230 MPa respectively. The ultimate tensile strength of the welded joint by FSW and UFSW (Al 6061/18 wt.% SiCecomposites) was 165 MPa and 180 MPa at rotation speed 1000 rpm respectively. The microstructural assessment showed that due to larger grain sizes at FSW and UFSW, most of the fractures are located in the thermal mechanically affected zone (TMAZ) adjacent to the weld nugget zone (WNZ). It is observed that in failure, most of the joints show ductile features. As the volume fraction of SiC (18 wt.%) increases, the friction stir welded and underwater friction stir welded efficiency decreases.

Keywords

• friction stir welding
• underwater friction stir welding
• aluminum matrix composites
• tensile strength
• microhardness
• microstructural analysis