Friction stir welding (FSW) is a relatively new solid-state joining process. This joining technique is energy efficient, environment friendly, and versatile. In particular, it can be used to join high-strength aerospace aluminum alloys and other metallic alloys that are hard to weld by conventional fusion welding. FSW is considered to be the most significant development in metal joining in a decade. Recently, friction stir processing (FSP) was developed for microstructural modification of metallic materials. In this review article, the current state of understanding and development of the FSW and FSP are addressed. Particular emphasis has been given to: (a) mechanisms responsible for the formation of welds and microstructural refinement, and (b) effects of FSW/FSP parameters on resultant microstructure and final mechanical properties. While the bulk of the information is related to aluminum alloys, important results are now available for other metals and alloys. At this stage, the technology diffusion has significantly outpaced the fundamental understanding of microstructural evolution and microstructure–property relationships.

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Friction Stir Welding and Processing

The comprehensive body of knowledge that has built up with respect to the friction stir welding (FSW) of aluminium alloys since the technique was invented in 1991 is reviewed The basic principles of FSW are described, including thermal history and metal flow, before discussing how process parameters affect the weld microstructure and the likelihood of entraining defects After introducing the characteristic macroscopic features, the microstructural development and related distribution of hardness are reviewed in some detail for the two classes of wrought aluminium alloy (non-heat-treatable and heat-treatable) Finally, the range of mechanical properties that can be achieved is discussed, including consideration of residual stress, fracture, fatigue and corrosion It is demonstrated that FSW of aluminium is becoming an increasingly mature technology with numerous commercial applications In spite of this, much remains to be learned about the process and opportunities for further research a

Friction stir welding of aluminium alloys

http://www.jwri.osaka-u.ac.jp/~dpt9/2017.pdf

Tensile properties and fracture locations of friction-stir-welded joints of 2017-T351 aluminum alloy

Friction stir welding/processing of metals and alloys: A comprehensive review on microstructural evolution

Development of grain structure during friction stir welding

The microstructure and texture of friction stir welded joints of hot mill stock 5754 and 5182 aluminium alloy sheets were examined after a commercial joining process. The as received sheet was cut into two pieces, one piece was cold rolled with 20 reduction in thickness, whereas the other was subsequently aged at 230C for 100 h after the 20 prestrain. These two pieces with different thermal pretreatments were joined by friction stir welding FSW. On FSW, a uniform fine grained microstructure in the through thickness of the sheet having a width corresponding to the diameter of tool shoulder was observed in both the 5754 and 5182 joints. Moreover, the microhardness profile did not reveal a softened heat affected zone between the weld and the base metal. An X-ray pole figure study showed that the 5754 and 5182 weld zones were not highly textured and both comprised of similar texture components. The calculated average sheet formability of the weld zones predicts a more isotropic behaviour than that for...

M. Ball

Papers

Characterisation of microstructure and texture in friction stir welded joints of 5754 and 5182 aluminium alloy sheets