Underwater friction stir welding of marine grade aluminium alloys: A review

Abstract

Aluminium alloys of the 5xxx and 6xxx types are considered marine grade alloys. These alloys are highly resistant to corrosive environments and are therefore used in maritime applications. However, joining these alloys by traditional welding process is a difficult task and can also lead to defect formations in the joints. Friction stir welding being a solid-state welding process uses a special type of tool to join workpieces at a temperature below the melting point of the material. This process saves a lot of energy, is eco-friendly and also yields better mechanical properties than the conventional fusion welding processes. However there is a decrease in the mechanical properties of the joints since the heat cycles involved in FSW can lead to softening of the joints. Underwater friction stir welding is a modification of FSW where welding is performed under the influence of a liquid medium like water. UFSW reduces the peak temperature of welding and produces better mechanical properties than the normal FSW process. A review of underwater friction stir welding of marine grade aluminium alloys is provided here. A review regarding the different parameters of the process, microstructure development, and corrosion resistance is discussed in this paper. From the review, it can be inferred that UFSW is very effective for joining marine grade aluminium alloys with minimal defects and better mechanical properties.