Open Access Conference Proceedings

Recycled aluminum in tailor-welded blanks (TWBs) offers sustainable solutions for automotive applications. However, variations in impurity levels, depending on the source of the scrap, negatively impact weldability with conventional fusion-based welding methods, limiting its usage compared to primary aluminum. This study aims to investigate how differences in microstructural and mechanical anisotropy between primary and recycled 6082-T6 aluminum alloys affect the mechanical integrity of TWBs joined through friction stir welding (FSW). The alloys differ in chemical composition, particularly with the recycled variant showing elevated levels of iron (Fe), copper (Cu), and zinc (Zn), which can significantly influence weldability, microstructure, and mechanical performance. Both alloys were welded together at a rotational speed of 1000 rpm and a welding speed of 60 mm/min, with weld line orientations of 0°, 45°, and 90° relative to the extrusion direction. Before welding, tensile tests were conducted to evaluate the strain characteristics in different directions, determining the alloys' mechanical anisotropy. Results show clear differences in the mechanical anisotropy between primary and recycled aluminum, primarily due to the variation in the distribution and density of intermetallic phases across the thickness. The stir zone (SZ) exhibited a reduced yield strength of 195 MPa, which resulted in an increased fracture strain of 29%. This is attributed to the dissolution of strengthening precipitates and the homogeneous distribution of intermetallic particles within the matrix. The recrystallized grains within the SZ were equiaxed and significantly finer than the base metals (BMs), with an average grain size of approximately 7 ± 3 µm compared to 20 ± 5 µm in the BMs. The hardness in the SZ was found to be significantly lower than in the BMs, with maximum hardness values ranging between 70 – 90 HV for all three orientations. However, the transverse tensile properties were largely unaffected by the weld line orientation, resulting in consistently lower strength and ductility values compared to those of the BMs.

Keywords: Friction stir welding, anisotropy, recycled aluminum, dynamic recrystallization

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