Papers by Keyword: Extrusion

Abstract: Nowadays, the growing demand for sustainable solutions in manufacturing has shifted research attention toward innovative recycling strategies. Among these, the Solid-State Recycling (SSR) technique has emerged as a viable approach to transform metal swarf into new products. Within the SSR family, friction stir extrusion (FSE) has gained particular interest as a promising method for producing wires from metal scraps, but recently, it was also employed for tube manufacturing. In literature, tube production via chip recycling often involves multi-step approaches, first consolidating/homogenizing the recycled chips and then extruding. In other cases, the tubes are manufactured directly from a bulk material, losing the sustainable goal. For this reason, this study aims to propose a single-step process in which aluminium chips are directly turned into a consolidated tube without any intermediate step. In addition, specific attention was given to the study of tool geometry, aiming to investigate the effect of a tapered tool’s shape on the material flow and the overall process performance. Experimental tests were conducted to characterize the microstructure of extruded tubes and to calibrate numerical simulations employed for investigating process dynamics. Results revealed that the reduced contact diameter of the chamfered tool generated lower processing temperatures but higher strain levels, fundamentally shifting the bonding mechanism from thermal assistance to mechanical dominance in oxide film breakage. Microstructural analysis demonstrated that the flat tool, characterized by predominant frictional heating and lower deformation, produced larger grain diameters due to thermally induced coarsening. Conversely, the chamfered tool yielded significantly refined grain structures through severe plastic deformation and dynamic recrystallization under suppressed thermal conditions, indicating superior consolidation quality and enhanced particle bonding.

Abstract: Efficient characterization of formability of tubal sections is essential for designing lightweight aluminum extrusion components, particularly since the presence of weld seams and extrusion-induced inhomogeneities influence deformation behavior. This study evaluates the formability of Al–Mg–Si alloy tubes after being subjected to four different heat-treatment conditions, using a non-conventional rubber-assisted bulge test. A solid polyurethane (PU) plug was employed as pressure medium to enable full-scale deformation. Digital image correlation (DIC) was used to quantify circumferential and longitudinal strain evolutions, while post-fracture thickness measurements provided complementary insight into through-thickness strain.The measured circumferential strain at fracture ranged from 0.15 to 0.24 across the investigated tempers. The W-tempered condition exhibited the highest surface strain while maintaining moderate thickness reduction, whereas the soft-annealed tubes showed the largest thinning. The as-received and naturally aged conditions displayed similar deformation responses. These results demonstrate that tube formability, as evaluated by the present testing approach, is characterized by the combined evolution of surface strain and thickness reduction, both of which are influenced by heat treatment. Overall, the study shows that PU-assisted rubber bulge testing provides a practical and robust experimental framework for the comparative assessment of formability in extruded aluminum tubes.

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: 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: Batteries are an important part of our everyday lives. They are used in many areas of life, such as watches, flashlights, fire alarms and other appliances, but also in infrastructure for storing energy in households or for emergency power. Metal-air batteries could be used in many of these energy storage scenarios. Magnesium (Mg)-air batteries, in particular, are a promising technology due to the large Mg deposits in the earth's crust and the relatively low extraction costs make them interesting as an alternative for other primary batteries. A weak point of Mg-air batteries is parasitic corrosion, in which hydrogen is released and additionally forms a passivation layer of Mg hydroxide which reduces the active surface. The parasitic corrosion depends on the type and concentration of the electrolyte. When using sodium chloride (NaCl) as an electrolyte, the concentration is decisive for the performance of the battery. During operation of the battery, the electrolyte is saturated with Mg hydroxide due to the discharge process and parasitic corrosion. The magnesium hydroxide (Mg (OH)₂) precipitates together with the NaCl and thus changes the concentration of the electrolyte, which leads to an uneven conduction of the ions. Thus, a new way of influencing the stabilisation of the electrolyte for Mg-air batteries was tested. For this purpose, anodes consisting of NaCl particles and Mg powder were produced by indirect extrusion. In order to investigate the functionality and application possibilities of this technology, the anodes were tested for their microstructure and performance compared to pure Mg and the conductivity of the electrolyte during the discharge of the battery. The influence of the salt particle size and the salt particle content was also investigated using different anodes and different electrolytes.

Abstract: 3D printing of ceramics grabbed its attention recently because of its ease of shaping. The extrusion-based 3D printing technique is widely used for ceramics as it involves paste formulation. However, the slurry is often formulated and mixed initially by hand kneading and later by a high-speed mixer. This phenomenon leads to the evaporation of water quickly while combining or out of its insufficient time allowed for extrudable slurry or paste formulation. The slurry's printable time is also reduced due to this phenomenon. This study prepares a hybrid ceramic mixture comprising silica gel, and printable time is calculated. Triaxial porcelain is used as a model ceramic.

Abstract: The lubricant thickness in cold forging was estimated by machine learning of the in situ captured images of the die–workpiece contact interface. The images were in situ captured by a high-speed camera from the backside of the transparent glass die during forging of commercially pure aluminum workpiece. On the other hand, the images of the lubricated workpiece were individually captured as training images for random forest with classification. The classification accuracy of the lubricant thickness was confirmed to be approximately 75% (classification ability: 5–10 μm in lubricant thickness) in the training images with 22,500 px (50 px/mm). The in situ captured images of the die–workpiece contact interface during forging were classified by random forest using the training images. The estimated lubricant thickness of the in situ captured image almost agreed with the lubricant thickness estimated from the mean brightness value of the in situ captured image.

Abstract: In this paper, a numerical simulation methodology has been applied to optimize the design of extruded aluminium products. The methodology, PRO^{3 TM} , incorporates product properties, production-and material costs as well as CO₂ footprint in an optimisation procedure. This allows for multi-objective optimisation and avoids sub-optimisation of for instance properties on the expense of production costs or CO₂ emissions. The outcome that follows from this multi-objective optimisation procedure, is that the resulting profile cross section will be different when the optimisation is based solely on property considerations, than when costs and CO₂ emissions are introduced in the optimisation procedure. The present methodology requires that the main processes and operations along the aluminium process chain are represented by physics based, predictive models of various types, including material-and mechanical models, in addition to cost-, and sustainability models. A standard multi-objective optimization algorithm is used to combine the models and for automatic running through-process simulations in iterations. In this article, the PRO^{3 TM} methodology has been applied for optimisation of the profile cross section in case-studies with various user requirements. It has been demonstrated that the resulting cross section geometry depends on the specified relative importance of conflicting requirements like the desire for high productivity on the one hand, and the desire for low material costs and low CO₂ emissions on the other.

Abstract: The paper presents the experience of development and implementation of an integrated approach of extrusion simulation with the automated design of the dies as a new way to speed up the technology development and its optimisation based on the QForm UK Extrusion simulation program and QForm Extrusion Die Designer (QExDD) design system. Bearing and prechamber optimisation types are considered for the porthole design. Welding quality and possible streaking lines in the profile are analysed for the tool construction with optimised prechamber contour.

Abstract: The velocity fields of axisymmetric direct extrusion of metals was analysed by the upper-bound method and compared with the results from the finite-volume method, FVM. The upper-bound technique proposed by Avitzur and by Zhao et al. together with the streamline functions were employed to calculate the analytical velocity fields, which consider the friction at die wall. Moreover, the components of strain-rate are also presented. Additionally, the axisymmetric extrusion process was modelled by the FVM method to calculate the velocity fields and compared with the Avitzur’s and by Zhao’s solutions. The FVM velocity fields were calculated by using the Eulerian approach of fixed grid, the governing equations of metal plastic flow and conservation laws discretized by the FVM and the Explicit MacCormack method in structured and collocated mesh were also employed. Friction at die wall was modelled by the friction factor model, using the tangential shear stress boundary conditions. The examined material experimental parameters were obtained from the Al 6351 aluminium alloy in the direct extrusion process at 450^o C. Velocity fields of the longitudinal and radial velocity distributions by the upper-bound and FVM methods are presented and compared. Good agreement is shown between the radial velocity component V_r from the Avitzur´s and FVM results, but poor for the longitudinal velocity V_z. From the analysis of velocity fields, the most severe condition of wear on the inner wall of the die and material surface damage occurs in the area near the exit corner of the die. However, the predicted location of the severe wear region in the die wall by the FVM method is located prior to the point predicted by the Avitzur model.