Effect of tool pin profile on the hook geometry and mechanical properties of a friction stir spot welded AA6082-T6 aluminum alloy

Abstract

AA6082-T6 alloy was joined by friction stir spot welding using five different pin profiles, such as a cylindrical, conical, triangular, hexagonal and cylindrical with two grooves, at different dwell time. The joints welded by cylindrical pins had larger effective weld width. But, grooves on the cylindrical pin decreased the effective weld width. The hook was bent downward from the interface of the sheets in the weld made with hexagonal pin, which had the smallest effective weld width. When conical pin was used, effective weld width increased with increasing the dwell time. In the case of using tools with cylindrical and conical pins, HAZ hardness was relatively lower. With increasing dwell time, HAZ hardness of the joints made with conical pin decreased. Effective weld width determined the weld strength under the tensile shear loading condition: Larger effective weld width resulted in higher weld strength. Weld strength of the joints made with cylindrical pin was higher. The joints fabricated with hexagonal pin had the lowest weld strength. In general, higher dwell time led to higher weld strength. The welds with the higher strength experienced both brittle and ductile fractures, while the joints with the lower strength exhibited completely brittle fracture.

A Novel Friction Stir Deposition Technique to Refill Keyhole of Friction Stir Spot Welded AA6082-T6 Dissimilar Joints of Different Sheet Thicknesses

“…In addition, they contain comparatively coarse (Fe, Mn) 3 SiAl l2 intermetallic and low-density fine dispersed Mg 2 Si precipitates. These microstructure features are consistent with that reported in other works [ 2 , 36 , 47 ]. It can be observed also that the AA 6082-T6 sheets of 1 ( Figure 11 a) and 2 mm ( Figure 11 b) thickness have average grain sizes of 11 ± 2 and 17 ± 1.5 μm, respectively.…”

“…In addition, they contain comparatively coarse (Fe, Mn)3SiAll2 intermetallic and low-density fine dispersed Mg2Si precipitates. These microstructure features are consistent with that reported in other works [2,36,47]. It can be observed also that the AA 6082-T6 sheets of 1 (Figure 11a) and 2 mm (Figure 11b) (a-d) the FSSW lap joints of AA6082-T6 welded at a constant dwell time of 3 s and different rotational speeds of 400 to 1000 rpm [36] and (e-h) RFSSW deposited at a 400 rpm rotation speed and a 1 mm/min deposition rate.…”

“…The TMAZ hardness gives lower values than the SZ and higher values than the HAZ. The increase in hardness of the TMAZ over the HAZ is likely due to the high dislocation density achieved by plastic deformation during the process of FSSW [ 14 , 47 ]. The highest hardness of the weld zones is achieved for the FSSWed joint at 600 rpm ( Figure 12 b).…”

Novel Technique for Design and Manufacture of Alternating Gradient Composite Structure of Aluminum Alloys Using Solid State Additive Manufacturing Technique

“…During the dwell time, the tool shoulder penetrates the top surface of the upper layer and the tool pin penetrates the top surface of the lower layer. This action supplies the driving power required for the upward movement of the materials in the lower layer as shown in Figure 6 b. Aydin et al [ 41 ] and Ji et al [ 42 ] reported similar outcomes. In addition, the creation of the kissing bond is due to the inadequate flow caused by the pin’s incomplete stirring.…”

Mechanical properties of AA6061T6 and AA6351T6 plates joined by friction stir welding

“…This was due to increased heat input, which results in effective material plasticization. This could be linked to the hardening precipitates becoming coarser due to the increased heat input, resulting in a higher hardness value [35]. Fine‐grain development strengthens grain boundaries by preventing dislocation motion during hardness indentation.…”