Effect of Shoulder Diameter on the Force Generation, Microstructure and Mechanical Properties of Friction Stir-Brazed Aluminium Alloy and Copper with Ultrahigh Rotation Speed

Abstract

Friction stir brazing with ultrahigh rotation speed was applied to 6061 aluminium alloy-pure copper lap joints with the aid of zinc foil. The effects of different shoulder diameters from 7 to 15 mm on the microstructure and mechanical properties of Al/Cu FSB joints were investigated along with the temperature and resistance of the friction tool. The oscillation of forward resistance and lateral force was related to the flow of the plastic metal and contributed to obtain a good appearance during the welding process. From the appearance of the welded joints, it was obvious that the phase difference between the forward resistance and lateral force had a significant influence on the joint characteristics. Obvious scale-like ripples appeared on the weld area when a sharp angle in the phase difference curve existed. Additionally, with a lower axial force and oscillation assistance, a satisfactory joint could be obtained. The results of the shear strength of the brazed joint showed that the shoulder with a 12 mm diameter yielded the highest shear strength. Meanwhile, the zinc foil in the middle melted completely and formed finely dispersed CuZn 5 Al-Zn eutectic structures at the Al-Cu interface.

Advances in simulation and experimental study on intermetallic formation and thermomechanical evolution of Al–Cu composite with Zn interlayer: Effect of spot pass and shoulder diameter during the pinless friction stir spot welding process

“…It has been known that the tool shoulder affects the heat input, material flow, plunge load, and stir action in the weld zone. 45 The effect of shoulder size on the macrostructure evolution of the joint interface as interlayer is applied during the joining process was analyzed by Zhou et al 46 They found that the interlayer thickness in the interface joining decreases with an increase in the shoulder diameters because of higher axial force and heat input. Akinlabi 47 reported that high intermixing between copper and aluminum materials with acceptable material flow patterns can be achieved with a tool shoulder of 15 and 18 mm diameters while using a shoulder with 20 mm diameters leads to the formation of improper material mixing in the joint zone.…”

A Review on the Friction Stir Brazing for Joining Dissimilar Materials

“…Y. Zhou et al [42] observed that the shear strength of Cu/Al joints increments and then decreases with augmenting shoulder diameter (Figure 12). Where the highest value of shear strength (18.67 MPa) is reported in a sample using a shoulder diameter of 12 mm, which is fractured in the heat affected zone for Al plates (Figure 12b).…”

FEM Analysis and Verification of Pinless Friction Stir Spot Welding of Cu and Al with Zn Interlayer: Effect of Shoulder Diameter and Spot Pass

“…It has been known that the tool shoulder affects the input heat, material flow, plunge load, and stir action in the weld zone [37]. The effect of shoulder size on macrostructure properties of the joint interface as interlayer is applied during the welding process was investigated by Zhou et al [38]. They found that the interlayer thickness in the interface joining decreases with the increase in the shoulder diameters due to higher input heat and axial force.…”