Key Takeaways & Executive Findings
- •• A novel forward needle penetration extrusion process enables precision manufacturing of large-sized seamless thin-walled cylindrical components with high-ribs, achieving superior material flow uniformity (SDV=0.478). • Optimal process parameters (billet 465°C, die 460°C, container 420°C, speed 1.5 mm/s) yield exceptional microstructural homogeneity compared to conventional porthole extrusion. • The process induces significant fragmentation of coarse secondary-phase particles and fibrous grain structures, with GDRX and DDRX as dominant recrystallization mechanisms. • Mechanical property variations across regions are within 7%, with rib head region exhibiting highest tensile strength (360 MPa) and yield strength (215 MPa), and all regions showing elongation >22%.
Abstract
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.
1. Introduction
Al−Zn−Mg−(Cu) alloys are favored in high-end aluminum applications owing to their excellent plasticity, high specific strength and stiffness, low density, excellent weldability, and significant heat-treatable strengthening potential [1−4]. These alloys are commonly used in aerospace, high-speed trains, advanced weaponry, and many other industrial fields [5,6]. Thin-walled, high-ribbed aluminum alloy profiles are key components for large rocket carrier wall panels [7,8], characterized by thin wall thickness, high rib-to-wall ratio, and high dimensional accuracy. Currently, conventional manufacturing processes for these profiles, include riveting or welding skins and stiffeners, milling thick plates, die forging, roll forming and spinning, etc [9,10]. However, these traditional methods suffer from significant drawbacks such as long production cycles, high costs, and limited manufacturing precision. By contrast, high-temperature extrusion involving severe plastic deformation offers substantial improvements in both manufacturing efficiency and structural performance. This process not only mitigates strength and fatigue degradation associated with riveting or welding but also reduces assembly-induced damage, thereby extending the service life of carrier wall panels.
Extrusion forming is a critical technique for manufacturing large, complex cross-sectional components, as it ensures high dimensional accuracy while simultaneously enhancing strength and ductility through extrusion-induced effects [11,12]. Nonetheless, challenges such as difficult material flow and uneven deformation often arise during extrusion, underscoring the importance of optimized process design and die configuration to achieve uniform properties.
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Hui LI, Cong CHANG, Hong-bang SHAO, Yuan-chun HUANG, Jun-hua CHENG (2025). Achieving uniform microstructure and properties in large-sized seamless thin-walled cylindrical components with high-ribs using novel forward needle penetration extrusion process. SinoTechIntel Verified Research. https://doi.org/10.1016/S1003-6326(25)67016-6
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Frequently Asked Questions
What is the novel forward needle penetration extrusion process?
It is an innovative extrusion die assembly designed to manufacture large-sized seamless thin-walled cylindrical components with high-ribs, achieving superior material flow uniformity and microstructural homogeneity compared to conventional methods.
What are the optimal process parameters for this extrusion process?
The optimal parameters are billet temperature of 465°C, die temperature of 460°C, container temperature of 420°C, and extrusion speed of 1.5 mm/s, resulting in a low standard deviation of velocity field (SDV) of 0.478.
How does this process affect the microstructure of Al-Zn-Mg alloy?
The process fragments coarse secondary-phase particles, flattens grains into fibrous shapes, and promotes geometric dynamic recrystallization (GDRX) and discontinuous dynamic recrystallization (DDRX), leading to uniform microstructure.
What are the mechanical properties of the extruded components?
Mechanical property variations across regions are within 7%, with the rib head region showing the highest tensile strength (360 MPa) and yield strength (215 MPa), and all regions exhibiting elongation exceeding 22%.
What are the advantages of this extrusion process over conventional porthole extrusion?
The developed method produces seamless components with superior microstructural homogeneity and more consistent mechanical properties, overcoming limitations of conventional porthole extrusion.
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