Abstract
Friction stir welding (FSW) is a promising welding method for welding dissimilar materials without using welding flux. In the present work, 5A06-H112 and 6061-T651 aluminium alloys were successfully welded by friction stir welding with forced air cooling (FAC) and natural cooling (NC). Nanoindentation tests and microstructure characterisations revealed that forced air cooling, which can accelerate the cooling process and suppress the coarsening of grains and the dissolution of precipitate phases, contributes to strengthening and narrowing the weakest area of the joint. The tensile strength of joints with FAC were commonly improved by 10% compared to those with NC. Scanning electron microscopy (SEM) images of the fracture surface elucidated that FSW with FAC tended to increase the number and reduce the size of the dimples. These results demonstrated the advantages of FSW with FAC in welding heat-sensitive materials and provide fresh insight into welding industries.
Highlights
Aluminium alloys have been widely used in the aviation, aerospace, shipping, and transportation industries because of their advantages of high specific strength, good fatigue performance, and strong corrosion resistance [1,2,3]
Due to the large amount of heat generated by friction and plastic deformation, the welded joint shows an obvious thermal softening effect, leading to the strength of the heat affected zone (HAZ) being lower than the base material (BM) [14,15]
Zhang et al [16] pointed out that the tensile strength and corrosion resistance of Friction stir welding (FSW) AA2014 joints were enhanced via water cooling
Summary
Aluminium alloys have been widely used in the aviation, aerospace, shipping, and transportation industries because of their advantages of high specific strength, good fatigue performance, and strong corrosion resistance [1,2,3]. Due to the large amount of heat generated by friction and plastic deformation, the welded joint shows an obvious thermal softening effect, leading to the strength of the HAZ being lower than the BM [14,15]. Taking this into account, a forced cooling medium was applied during the welding process to reduce the thermal softening and improve the strength of the joint. Benavides et al [18] investigated the mechanical properties of FSW
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