In-Process Cooling in Friction Stir Welding of Aluminium Alloys—An Overview

Friction stir welding (FSW) is a welding technique that has found extensive use in the joining of aluminium alloys for many applications. During FSW welding, severe plastic deformation occurs due to the stirring actions of the tool which generates heat on the workpiece. The thermal cycle set up at the weld region causes deterioration of precipitates by coarsening or dissolutions. The resultant mechanical properties of the weld region, therefore, become lesser than that of the base metal. Efforts have been made by various researchers to address this challenge through in-process cooling using different cooling fluids such as cryogenic, slush ice, water, compressed air and liquified nitrogen to control the temperature during FSW so as to enhance the mechanical behavior of the welds. The in-process cooling approach was generally reported to have improved the mechanical and corrosion behavior of welded joints as a result of fine and stable microstructures obtained at the weld zone. This paper reviewed the research efforts in this direction. The authors and their investigations and findings have been briefly summarized and the influence of these cooling media on tensile, microstructures and corrosion behavior has been highlighted. The overall aim of this review paper is to provide comprehensive requisite knowledge of the current state of research on in-process cooling in FSW of aluminium alloys with a view to exposing further areas of research interest in this aspect of FSW.