Friction Stir Welding of Aluminum in the Aerospace Industry: The Current Progress and State-of-the-Art Review

Abstract

The use of the friction stir welding (FSW) process as a relatively new solid-state welding technology in the aerospace industry has pushed forward several developments in different related aspects of this strategic industry. In terms of the FSW process itself, due to the geometric limitations involved in the conventional FSW process, many variants have been required over time to suit the different types of geometries and structures, which has resulted in the development of numerous variants such as refill friction stir spot welding (RFSSW), stationary shoulder friction stir welding (SSFSW), and bobbin tool friction stir welding (BTFSW). In terms of FSW machines, significant development has occurred in the new design and adaptation of the existing machining equipment through the use of their structures or the new and specially designed FSW heads. In terms of the most used materials in the aerospace industry, there has been development of new high strength-to-weight ratios such as the 3rd generation aluminum–lithium alloys that have become successfully weldable by FSW with fewer welding defects and a significant improvement in the weld quality and geometric accuracy. The purpose of this article is to summarize the state of knowledge regarding the application of the FSW process to join materials used in the aerospace industry and to identify gaps in the state of the art. This work describes the fundamental techniques and tools necessary to make soundly welded joints. Typical applications of FSW processes are surveyed, including friction stir spot welding, RFSSW, SSFSW, BTFSW, and underwater FSW. Conclusions and suggestions for future development are proposed.

Additively Manufactured Parts from AA2011-T6 Large-Diameter Feedstocks Using Friction Stir Deposition

“…A homogenous fine equiaxed grain structure has been detected at all the applied conditions due to the dynamic recrystallization during the additive-manufacturing-based friction techniques [54]. Friction-based processes (FSW, FSP, and A-FSD) contribute to increasing the temperature of the processed material in the stirring zone to temperatures that may reach, under the control of the processing parameters, between 60% and 80% of the material's melting point, which is high enough for recrystallization during the intensive plastic deformation [49][50][51]. The optical microscopy investigation was carried out on long transverse cross-sections of the FSDPs.…”

Prediction of Tool Eccentricity Effects on the Mechanical Properties of Friction Stir Welded AA5754-H24 Aluminum Alloy Using ANN Model

“…In order to predict the impact of pin eccentricity on the mechanical properties of AA 5754-H24 FSW aluminium alloys and to identify the ideal conditions for input parameters to produce FSW joints with good mechanical properties, computer-aided ANN modelling has recently become widely used in the field of friction stir welding [ 4 , 31 , 36 , 37 , 38 ]. Many publications are found in the literature on FSW of aluminum alloys, focusing on the correlation between the friction stir welding parameters and the mechanical properties [ 31 , 39 ].…”

Influence of the Duration and Temperature of the Al-Fin Process for the Cast Iron Insert on the Microstructure of the Bimetallic Joint Obtained in the Piston Casting Process

“…Although many methods have been developed to join aluminium with aluminium and aluminium with Fe-based alloys, such as rolling [33], riveting [34], conventional laser welding [35,36], high-speed fibre laser welding [37], oscillating laser welding [38] and friction stir welding [39,40] it is hard to claim that these methods are easy to implement when joining elements with complex-shaped components [41]. The casting process, by means of which liquid metals can be joined with solid metals in the metallurgical process, has great flexibility when joining elements with complex shapes [42].…”