Mechanical and microstructural properties evolutions of various alloys welded through cooling assisted friction-stir welding: A review

Friction stir welding (FSW) exhibit high rate of plastic deformation thereby microstructure modification through intense coarsening and grain boundary precipitation found in the weld zone. The microstructure and microchemistry of the weld can be controlled by cooling assisted friction stir welding (CFSW) with minimizing peak temperature and heat input thereby better efficiency and performance of joint produced. This becomes more considerable especially during dissimilar material joining due to variations in thermo-mechanical properties and chemical compositions of material. The joint efficiency can also be enhanced by suppressing the intermetallic compounds (IMCs) formation and controlling the grain growth by applying cooling medium (i.e. compressed air, water, carbon dioxide (CO2) and liquid nitrogen). This article reviews the current status of on-going research in CFSW. The particular attention has been paid to process parameters, phase transformation, texture evolution, recrystallization mechanism, microstructural behaviour, and the influence of these factors on the joint tensile strength, hardness, fatigue properties, residual stresses as well as corrosion behaviour. And also, new research directions in this field have been proposed for upcoming research. [Display omitted] •Cooling-assisted friction stir welding (CFSW).•Water, Compressed air, CO2, and Liquid nitrogen have been used as cooling medium.•Influence of welding parameters and cooling medium on peak temperature and hence the weld properties.•Microstructural characterization and IMCs formation phenomenon have been discussed.•Mechanical properties have been enhanced comparing to conventional FSW.