Key Engineering Materials

Preface

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048

Mechanical Evaluation of 6060 Aluminum Alloy under Elevated Extrusion Ram Speed Using Liquid Nitrogen Die Cooling

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Evangelos Giarmas, Emmanouil K. Tzimtzimis, Konstantinos Tsongas, Dimitrios Tzetzis
This research explores the effect of elevated extrusion ram speed—achieved through die cooling with liquid nitrogen—on the mechanical behavior of 6060-aluminum alloy profiles. Mechanical characterization was conducted via tensile testing and nanoindentation, with the latter also employed to assess the alloy’s creep response. Results reveal that while the increased ram speed exerts minimal impact on Ultimate Tensile Strength (UTS) and Yield Tensile Strength (YTS), it notably enhances elongation. Furthermore, the study demonstrates a significant influence of ram speed on creep displacement as the dislocations generated by higher ram speeds seems to improve the creep resistance of the material. Keywords: 6060 Aluminum Alloy; Liquid Nitrogen Cooling; Nanoindentation; Tensile Testing; Creep Behavior.

An Experimental Investigation of the Effect of Compression Calibration on the Ductility of AA6061 Extrusions

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Mustafa Can Uzun, Togeir Welo
The growing use of extruded aluminum components in vehicle structures necessitates both strength and ductility to meet energy absorption requirements. In this study, a new compression calibration method for multi-chamber, hollow sections was developed with the aim of improving dimensional accuracy while enhancing the ductility of AA6061 extruded profiles. The influence of this method on mechanical properties was investigated through uniaxial tensile tests, three-point VDA bending tests, and axial crush tests. The uniaxial tensile test results revealed a reduction in the (logarithmic) strain at necking, while no significant changes were observed in yield and ultimate tensile strengths. On the other hand, the VDA tests showed a systematic increase in the normalized bending angle, indicating improved energy absorption characteristics. Visual inspection and the absorbed energy obtained by axial crush tests supported the findings in the VDA tests, indicating the compression calibration method enhances the crushability of extruded AA6061 profiles, although this improvement is not identified in standard tensile data. Overall, this work introduces a new, industrial calibration method for hollow extrusions that also enhances crushability.

Numerical Investigation of Round Profile Production: A Fem-Based Comparison between Friction Stir Extrusion and Conventional Extrusion

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Carlo Acerbi, Marco Negozio, Adrian H.A. Lutey, Matteo Felci, Uceu F.H. Suhuddin, Harikrishna Sinh Rana, Benjamin Klusemann, Sara Bocchi
Friction Stir Extrusion (FSE), Direct Extrusion (DE) and Indirect Extrusion (IE) are all valid processes for the production of round profiles. However, differences and similarities between them have yet to be analyzed by the scientific community, since with the same geometry, each technology instills specific properties to the extruded product. In this context, the present work proposes an in-depth analysis via QForm UK Finite Element Method (FEM) software of the effect that each process has on a AA6061 extruded wire. Various combinations of rotational speed (200, 400, 600 rpm), feed rate (1, 2, 3, 4 mm/s) and pre-heating temperature (450, 500°C) were analyzed to assess differences and similarities between FSE, DE and IE. The feedstock material for FSE was chosen to be powder, while a solid billet was used for conventional extrusion.

Compensating Property Fluctuations in Cold Extrusion Using Adaptive Dies

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Christian Siedbürger, Peter Groche
This study investigates an adaptive die concept for cold extrusion that actively modulates radial preload during the main forming and ejection phases. A Gaussian process regression (GPR) surrogate, trained on fewer than 400 finite-element simulations, provides a highly data-efficient model capable of accurately predicting geometric tolerances, residual stresses, and process forces. Experimental spot measurements validate the physical trends captured by the surrogate, demonstrating reliable reproduction of the underlying mechanical interactions. The results show that increased preload during forming enables micrometer-level calibration of final diameters, while higher preload during ejection promotes beneficial compressive residual stresses at the cost of elevated ejector forces. A part-to-part control strategy effectively improves accuracy by independently steering two target properties through separate preload adjustments. Furthermore, a reinforcement learning-based controller, enhanced by flow stress estimates derived from hardness measurements, reduces variance and compensates for stochastic fluctuations in material and friction conditions. Overall, the adaptive die system, combined with surrogate-and RL-based control provides a robust foundation for achieving high dimensional precision and stable product properties under future variability scenarios, such as green steel and sustainable lubrication systems.

Lightweight Battery Housings from Thin-Walled, Large-Scale Aluminum Profiles by Hot Extrusion

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Oliver Schulz, Sebastian Wurth, Alessandro Selvaggio, Johannes Gebhard, Yannis P. Korkolis, Patrik Bieker, Thomas Kloppenborg
The transition towards sustainable mobility demands lightweight and modular carrier systems for high-voltage batteries and fuel cells that combine structural efficiency with effective thermal management. This study examines the feasibility of producing thin-walled, large-scale aluminum extrusion profiles for modular battery housings using AA6063. Numerical simulations and experimental trials are conducted to optimize die design and define process limits along the relation between circumscribing circle diameter (CCD) and minimal wall thickness tmin. Furthermore, different quenching methods are used to investigate the influence on surface distortion and final mechanical properties. A streamlined die design with reduced mandrel deflection has enabled defect-free extrusion under controlled conditions for the extrusion of a thin-walled, large-scale profile with a CCD-to-tmin ratio of 138. A narrow process window is identified for extrusion of defect-free profiles. Quenching studies have shown that active cooling methods affect surface deformation but have negligible influence on mechanical properties or microstructure due to efficient heat extraction inherent to thin-wall geometries for the investigated alloy. Scaling experiments using an enlarged cross section by a factor of 2.5 have confirmed similar process stability without wall thickness adjustments, achieving up to 38 % weight reduction compared with conventional designs under industrial conditions.

Calibrating a Lode-Parameter-Dependent Damage Evolution Equation to Cold Extrusion Experiments

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Robin Gitschel, A. Erman Tekkaya, Yannis P. Korkolis
Forming processes significantly influence the product properties of a formed workpiece. Next to the effects of work hardening and residual stresses, the influence of ductile damage determines the final performance of a formed component. Thus, precise damage models are crucial for designing new forming process sequences. In general, this is achieved by modelling the evolution of damage as a function of hydrostatic and deviatoric stress, characterized by the stress triaxiality and the Lode-parameter. However, calibrating damage models to the effects of triaxiality and the Lode-parameter is not trivial, since experiments usually represent a combination of both influences. A recent experimental approach by the authors offers the possibility to vary the Lode-parameter in extrusion experiments while keeping the triaxiality constant. This paper aims to use this data of the isolated deviatoric effect on damage to calibrate a damage evolution equation. The model is calibrated to void area fraction measurements obtained by scanning electron microscopy of extruded case-hardening steel 16MnCrS5. For validation, the model predictions for non-constant Lode-parameter histories are compared to corresponding experiments. The model and experiments are in good agreement.

Effect of Chemical Composition on Hot Extrudability and Tribological Behavior of 7000 Series Aluminum Alloys

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Sukunthakan Ngernbamrung, Kuniaki Dohda, Tatsuya Funazuka, Junichi Oshima, Tomomi Shiratori
Aluminum 7000 series alloys are widely used for aerospace and transportation applications due to their high strength-to-weight ratio. This research investigates the impact of zinc (Zn) and magnesium (Mg) content on the hot extrudability and tribological behavior. Elemental quantities straight away impact flow stress, determining the manufacturing parameters, whereas galling and adhesion frequently degrade tool life. This work illustrates that by assessing essential ram speeds and temperature limits, adjusting Zn and Mg concentrations considerably improves the extrudability limit. A decreasing flow stress during deformation reduces micro-cracking tendency and improves surface quality. The findings provide critical compositional guidelines for high-strength aluminum alloys, effectively balancing processing efficiency with improved surface quality and reduced element adhesion behavior, ensuring better industrial outcomes for advanced structural components.

Using Tungsten Inert Gas Welding Equipment to Locally Heat Tubes and Achieve Inhomogeneous Thickness in Tube Sinking Processes

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Lemopi Isidore Besong, Johannes Buhl
Abstract. Tubes with non-uniform thickness are needed to even out wall thickness in draw bending and provide higher stiffness in specific directions in some applications. Tailored local heating of the tubes in tube sinking operations should reduce the local flow stresses and facilitate differential deformation along the circumference of tubes to form tubes with uneven wall thicknesses. Local heating of tubes prior to entry into the die in tube sinking is implemented in this research to form tubes with higher thickness in desired directions. Initial experiments are conducted using plasma heating by tungsten inert gas (TIG) welding equipment on EN AW 6060 AlMgSi0.5 aluminum tubes. The process window is described by varying the process temperature (weld current between 50 A and 80 A) while altering the degree of deformation, the tube diameter, and tube thickness. Tubes with no defects were formed at 50 A. Increasing the weld current led to a higher wall thickness (up to 25% thickness increase), however, high weld currents also favored the formation of surface defects, wrinkle formation, or burn-through holes depending on the process setup. The process window was larger for tubes with higher wall thickness.

Charge Weld Evolution in Profile Extrusion: Variability across Billets and Multi-Profile Designs

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Ivan Kniazkin, Ivan Kulakov, Nikolay Biba
Transverse (charge) welds form during billet transitions in aluminium extrusion when incoming material progressively replaces residual metal inside the die, defining the length of extrudate that must be scrapped. This study aimed to quantify charge weld evolution under industrially relevant conditions that are often underestimated in scrap length assessment, including multi-cavity flow imbalance, non-symmetric multi-profile placement, and billet-to-billet thermal stabilisation effects. Three case studies were analysed using finite element simulation in QForm UK: (i) the International Extrusion Benchmark 2023 multicavity die producing three hollow tubes with intentionally varied port and bearing designs, (ii) an industrial two-profile die with translated (non-mirrored) profile positioning to avoid post-extrusion rotation, and (iii) a complex industrial profile extruded over multiple consecutive billets. The benchmark study demonstrated strong agreement between simulation and experimental charge weld evolution for two profiles, supporting the reliability of the predicted cavity-dependent differences driven by port volume. In the translated two-profile configuration, the charge weld cut length required for full purity increased from 1674 mm to 1940 mm (+16.0%), and by +15.9% under the 95% industrial criterion (1458.1 mm vs 1690.7 mm). Billet-to-billet variability was substantial, with charge weld length increasing by +70.1% from the first to the fifth billet (2819.0 mm to 4791.7 mm), before stabilising. Overall, the results show that charge weld length is governed by residence-time differences through ports and flow channels, requiring profile-specific assessment and consideration of process stabilisation. In this context, FE simulation provides an effective means to localise the mixed zone and to support die optimisation strategies aimed at reducing scrap.

Development of a System for Ultrasonic Die Oscillations during Extrusion of Aluminum Hollow Profiles

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Tamara Thomas, Maik Negendank, Nico Laengst, Verena Merklinger, Joachim Maier, Soeren Mueller
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.

Detection of Charge Welds in Lateral Angular Co-Extrusion Using Non-Destructive Testing

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Alexej Verschinin, Florian Patrick Schäfke, Norman Mohnfeld, Hans Jürgen Maier, Johanna Uhe, Christian Klose, Sebastian Barton
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.

Comparative Characterization through Torsion Tests of Primary and Secondary Aluminum Alloys for the Extrusion Process

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Nicola Lai, Sara Di Donato, Lorenzo Donati, Riccardo Pelaccia, Barbara Reggiani, Marco Negozio
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.

Transient Thermal Analysis of Multiple Extrusion Runs with Nitrogen Cooling by Means of Qform Code

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Riccardo Pelaccia, Sara Di Donato, Marco Negozio, Nicola Lai, Barbara Reggiani, Lorenzo Donati
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.

Numerical Data-Driven Modelling of Modified Samanta Process for Cold Extrusion of Gears

Tue, 14 Apr 2026 00:00:00 +0200

Publication date: 14 April 2026
Source: Key Engineering Materials Vol. 1048
Author(s): Tahsin Deliktas, Marcel Görz, Adrian Schenek, Marco Speth, Mathias Liewald
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.