Key Engineering Materials Vol. 1048

Abstract: High friction in aluminum hollow profile extrusion limits material flow, process stability, and productivity. Ultrasonic vibration offers a promising approach to reduce friction, yet its application to industrial porthole dies is still insufficiently explored. This study presents the development and investigation of an ultrasonic die sonication system for aluminum extrusion. Finite element extrusion simulations demonstrate that reduced friction leads to lower extrusion forces, decreased profile exit temperatures, and improved material flow. A modified porthole die enabling ultrasonic excitation at multiple positions was designed accordingly. The vibrational behavior of the die was analyzed using three-dimensional modal and harmonic finite element simulations. Suitable excitation frequencies between 18.5 and 23 kHz were identified and experimentally validated by laser vibrometry, confirming effective transmission of ultrasonic vibrations into the die. The simulation results demonstrate the feasibility of ultrasonic die oscillation for aluminum hollow profile extrusion and provide a solid basis for forthcoming extrusion trials and further process optimization. The system was implemented, approved, and is now available for upcoming experimental trials.

Abstract: Although extrusion is a well-established and widely used manufacturing process, charge weld seams remain a persistent challenge due to oxides, contaminants, and unfavorable material flow conditions at billet-to-billet transitions. In lateral angular co-extrusion (LACE), the material flow becomes more complex because it is redirected orthogonally to the ram movement and the metal is segmented into four separate streams in the die. This results in charge weld seams developing in more intricate shapes and locations than in conventional forward extrusion. Knowing the position of these seams along the profile is therefore essential for ensuring the structural integrity of co-extruded hybrid profiles, such as aluminum alloy hollow profiles reinforced by an inner titanium alloy tube. This study investigated the formation of charge weld seams in LACE through controlled billet-on-billet experiments. A hybrid profile was produced consisting of EN AW-6082 aluminum alloy as the lightweight component and a reinforcement element made of titanium grade 5 (Ti-6Al-4V). To enable accurate detection of the charge weld seam within the aluminum alloy part of the profile using non-destructive testing methods, a thin iron foil was inserted as a robust marker prior to extrusion between two parts of a split billet. Eddy-current testing (ET) and ultrasonic testing (UT) were applied to detect and map the charge weld seam along the extruded profile. ET enabled robust, high-resolution circumferential mapping of the weld propagation, while UT provided depth-resolved information. Complementary cross sections were prepared to validate the NDT results and characterize seam morphology. This combined approach provides a clearer picture of the formation of charge weld seams in LACE and demonstrates that NDT techniques can be used to reliably identify and assess these features in complex hybrid profiles.

Abstract: In the transition to a circular economy in the automotive sector, it is essential to integrate recycled (or secondary) aluminum alloys into extrusion processes, while ensuring that their performance is as close as possible to that of primary alloys. Within the Horizon Europe ZEvRA project, this study aims to analyze and investigate the hot deformation behavior of four aluminum alloys, two primary alloys (AA6082 Primary and AA7108) and two recycled alloys (AA6082 Recycled and AA6061), in order to demonstrate their potential suitability for automotive applications. Hot torsion tests were conducted under temperature and strain rate conditions representative of industrial extrusion processes. Four different temperatures (400, 450, 500, and 550 °C) and four different strain rates (0.01, 0.1, 1, and 10 s⁻¹) were investigated, allowing the achievement of significantly higher strain levels compared to conventional standard tensile and compression tests. Subsequently, the flow stress curves obtained from the torsion tests were analyzed to evaluate the influence of temperature and strain rate on the plastic deformation behavior of the material and on the associated dynamic softening mechanisms. The results demonstrate a comparable deformation behavior between primary and secondary alloys, confirming the feasibility and full compatibility of recycled alloys for high-performance industrial extrusion applications. Furthermore, the experimental results provide a solid basis for the development of robust constitutive models to support FEM simulations aimed at optimizing metal forming pocesses within a circular manufacturing framework.

Abstract: In hot extrusion of light alloys, nitrogen cooling has become a strategic solution to mitigate thermal issues from high deformation rates and frictional heating, improving surface quality, extrusion speed, and die life. However, current cooling system designs remain largely empirical, and the limited use of predictive modeling and experimental monitoring often leads to inconsistent evaluations. This work proposes a dual-step procedure for transient numerical analysis of multiple billets with nitrogen cooling. First, a 1D numerical model of nitrogen cooling is simulated in a simplified environment reproducing extrusion thermal conditions, requiring negligible computational time. The resulting heat transfer coefficient (HTC) and nitrogen temperature are then integrated into the process model, implemented in Qform code, as additional boundary conditions. This approach enables the fully 3D extrusion model to account for nitrogen cooling effects not only on thermal gradients but also on aluminium flow and die resistance. A porthole die with three tube-shaped openings for hollow profile extrusion was experimentally tested under cooled and uncooled conditions, with thermal behaviour monitored by eleven thermocouples within the tooling set. Experimental–numerical comparison confirmed the advantages of numerical simulation for cooling channel design and the limitations of experience-based approaches.

Abstract: The Guided Material Flow (GMF) process is an advanced variant of the Samanta process designed for the net shape cold extrusion of gears. The GMF process employs a modified die geometry to control material flow and significantly reduce maximum tool loads, effectively overcoming traditional process limitations. Key advantages include enhanced tooth tip strength and a reduction in face end deformations, which are characteristic defects in the conventional Samanta process. Minimising these deformations reduces the requirement for subsequent machining and enhances overall material efficiency. A numerical dataset was generated to train and validate data driven surrogate models, facilitating rapid process analysis without the computational cost of continuous Finite Element Analysis (FEA). The models developed in this paper enable the precise prediction of critical process outputs, including maximum punch force, die filling behaviour, material utilisation and strain hardening at the tooth tip. This paper details the numerical data acquisition, the specific training and validation methodologies of the machine learning models and demonstrates their capability to accurately predict complex process outcomes when varying the geometry of the die active surface in the GMF process.