*2.5. Mechanical Testing*

Tensile tests were carried out for all geometries to determine the tensile strength and to evaluate the bonding strength. For each geometry two samples were tested on a Zwick Z250 kN (ZwickRoell GmbH & Co. KG, Ulm, Germany) with the preload force of 300 N, the clamping pressure of 30 MPa and the strain rate of 0.002 s<sup>−</sup>1. The geometry of the tested tensile specimen is depicted in Figure 4, which was manufactured out of the friction welding products with a reduced diameter for the gauge length. The joining zone is not located at the center of the tensile specimens due to the geometry of the welding products. Besides the decentralized joining zone, the results of the tensile tests reveal no irregularities, since necking did not occur or was located within the gauge length.

**Figure 4.** Geometry of tensile samples with highlighted position of the joining zone, according to DIN EN ISO 6892-1 [18], in millimeters.
