Experimental and Numerical Study on Friction Stir Back Extrusion of Recycled AA7020/Al₂O₃ Composite Rods

In this research, the production of composite rods from recycled AA7020 alloy chips together with Al₂O₃ reinforcing particles (average particle size of 1 µm) was investigated experimentally and numerically via the friction stir back extrusion (FSBE) method. The die and punch were made of H13 steel, and heat treatment and nitriding were applied to increase wear resistance. The FSBE process was optimized at a rotational speed of 450 rpm and a feed rate of 10 mm/min. Specimens were fabricated with Al₂O₃ weight percentages of 0, 0.5, 0.75, 1, and 2%. The results showed that the addition of particles up to 1 wt.% increased the yield strength to 300 MPa and the ultimate tensile strength to 378 MPa, while increasing the content to 2 wt.% reduced these values to 250 MPa and 300 MPa, respectively. The hardness of the specimens increased from 92 HB (for the specimen without particles) to 105 HB (for the 2 wt.% specimen). Finite element simulation using DEFORM software showed good agreement with experimental results (temperature of 390–400°C). This method offers a low-energy and sustainable approach for the direct production of composite rods from aluminum scrap.