An innovative forward needle penetration extrusion die assembly was designed, which enabled precision manufacturing of large-sized seamless Al−Zn−Mg alloy thin-walled cylindrical components with high-ribs. Through systematic numerical simulation and experimental validation, optimal process parameters were established (billet temperature of 465 °C, die temperature of 460 °C, container temperature of 420 °C, and extrusion speed of 1.5 mm/s), achieving exceptional material flow uniformity with a low standard deviation of the velocity field (SDV) of 0.478 at the bearing cross-section. The developed method produces seamless components exhibiting superior microstructural homogeneity compared to conventional porthole extrusion. Coarse secondary-phase particles are significantly fragmented after extrusion deformation, and grains are flattened into fibrous shapes, with the predominant recrystallization mechanisms being geometric dynamic recrystallization (GDRX) and discontinuous dynamic recrystallization (DDRX). Mechanical property variations across different regions are controlled within 7%, with the rib head region showing the highest tensile strength and yield strength, reaching 360 MPa and 215 MPa, respectively. Additionally, all regions exhibit elongation values exceeding 22%, indicating consistent ductility throughout the structure.
Li et al. (Wed,) studied this question.
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