Abstract

Review on Underwater Friction Stir Welding of Aluminum Alloys

Author(s): Vikrant Saumitra*, Yuvraj Singh and Shubham Kumar Ekghara

Underwater friction stir welding is an innovative and novel technique of welding. In this present era, very few researchers and academicians have done research on it. Research on underwater friction stir welding can boost and pave the way for the research area in the field of friction stir welding. Joining using fusion welding processes, results in the formation of solidification defects like porosity, alloy segregation, and hot cracking. To overcome the solidification related problems, solid-state welding processes such as Friction Stir Welding (FSW) prove useful. Though the joining takes place below the melting temperature of the material, the thermal cycle experienced by the Thermo-Mechanical Affected Zone (TMAZ) and Heat Affected Zone (HAZ) is causing grain coarsening and precipitates dissolution, which deteriorates the joint properties resulting in poor mechanical and physical behavior. To get rid of this problem, the Underwater Friction Stir Welding (UWFSW) process can be employed. The water cooling reduces the heat, and thus, the desired thermal softening takes place in TMAZ and HAZ. Therefore, the material flow is entirely different in FSW and UWFSW. Since the weld defects, microstructural evolution, and mechanical properties are closely related to the material flow behavior during welding so it is important to control the material flow and heat distribution during joining.

UWFSW has been demonstrated to be a promising method for strength improvement of normal FSW joints. However, when improper welding parameters are used then welding defects, such as voids can be produced in the joints, leading to dramatically deteriorated mechanical properties. Thus to obtain high quality underwater joints, it is necessary to understand the variables that promote the formation of these defects. So, to overcome these defects appropriate and optimum parameters are required. The majorsignificance of underwater FSW is in the field of lightweight alloys such as Aluminum alloys and Magnesium alloys. However, its application to metals such as steel, nickel and titanium has been also increasing.