Welding and processing of metallic materials by using friction stir technique: A review

Friction stir technique played a vital role in recent industries as it has been utilized in welding and processing of metallic materials. Friction stir welding (FSW) is applied for joining the poorly weldable materials and enhancing the microstructure and the mechanical properties of the welded joints. Friction stir spot welding (FSSW), underwater friction stir welding (UFSW) and vertical compensation friction stir welding (VCFSW) are variants of FSW process. On the other hand, friction stir processing (FSP) is another method, whose basic principal originated from friction stirring technique, which can be utilized for manipulating the base materials by performing dynamic recrystallization on grains resulting in superior properties of the processed material. Friction stir alloying (FSA) is analogous to FSP with implanted reinforcement particles, producing surface composites. Like other fusion welding techniques, FSW process has its own defects which especially characterize the friction stir welded joints. Tunnels, voids, flash, lack of penetration, kissing bond and surface grooving are the common defects of FSW method. Since friction stirring action generates both thermal and mechanical loads beside the higher plastic deformation, finite element modeling (FEM) has been used in model and simulation this of the process. A few research gaps are pin pointed and some research recommendations are included.