Feasibility study on application of hot forming quenching to patchwork blanks using two-stage refilled friction stir spot welding

Application of hot forming quenching on patchwork blank using two-stage refilled friction stir spot welding

MATEC Web of Conferences ◽

10.1051/matecconf/201818500028 ◽

2018 ◽

Vol 185 ◽

pp. 00028

Author(s):

D.S. Jo ◽

J.H. Kim ◽

D.C. Ko ◽

B.M. Kim

Keyword(s):

Process Parameters ◽

Spot Welding ◽

Weld Zone ◽

Friction Stir Spot Welding ◽

Hot Forming ◽

Two Stage ◽

Cold Forming ◽

Friction Stir ◽

Heat Treated ◽

Two Stages

The purpose of this study is to apply Hot Forming Quenching (HFQ) on Patchwork Blank of AA6061 using Two-stage refilled Friction Stir Spot Welding (TFSSW). TFSSW is a developed joining method to improve joint strength of conventional Friction Stir Spot Welding (FSSW) and it consists of two stages. The first stage is a conventional FSSW process and second stage is a refilling process for refilling keyhole. The Design of Experiment (DOE) was used to optimize the TFSSW process parameters. A hat shape forming test was performed using a patchwork blank manufactured with the optimal process parameters to investigate validity of applying HFQ. Formed hat shape part was sequentially heat treated with artificial aging (T6) condition. The hardness of the weld zone was measured to confirm a drop of mechanical property in comparison with the conventional cold forming, which shows the validity of HFQ application to patchwork blank using TFSSW.

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Friction Stir Spot Welding of AA2024-T3 with Modified Refill Technique

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.835.274 ◽

2020 ◽

Vol 835 ◽

pp. 274-287

Author(s):

Mahmoud Hussin Fahmy ◽

Hamed A. Abdel-Aleem ◽

Nahid Ahmed Abdel-Elraheem ◽

M.R. El-Kousy

Keyword(s):

Spot Welding ◽

Metal Flow ◽

Vertical Direction ◽

Friction Stir Spot Welding ◽

Weld Strength ◽

Al Alloy ◽

Exit Hole ◽

Two Stage ◽

Friction Stir ◽

Second Stage

The quality of welded joints of FSSW is mainly dependent on the processing parameters while the main disadvantage of this process is the creation of an exit hole. Process parameters, namely tool dimensions, tool rotational speed, and stir time were changed and their impact on bond dimensions and weld strength was investigated using 2024-T3 Al Alloy. Macro- and microstructures of the welded samples were examined; shear fracture loads were measured and the optimum set of operation variables was determined. To decrease the exit hole of the first stage the present paper proposes a modified two-stage weld-refill process employing the same welding machine. In this work, this two-stage process was referred to as reversed friction stir spot welding (ReFSSW). In the second stage, a smaller pin was used and the shoulder diameter was designed such that to force the metal of the upper plate to flow towards the exit hole of the first stage decreasing its dimensions. The metal flow in the second stage was evaluated by examining the microstructure of the metal that filled the exit hole of the first stage. Thin stir zone was found around the pin of the second stage followed by thermomechanically affected zone consisting of grains elongated in the vertical direction. The proposed process resulted in smaller exit hole dimensions and consequently higher mechanical properties compared with the conventional single-stage FSSW.

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