Axel von Hehl

• Prof. Dr.-Ing.
• Chair of Materials Science and Testing at University of Siegen, Germany

This report investigates the correlation between part geometry and the mechanical properties of 316L manufactured by laser powder bed fusion (PBF-LB/M). In a first step the manufacturing of different specimen geometries by PBF-LB/M was compared using a simulation. It was determined that differences of more than 300 °C occur between the average spec...

Smart-Alloying enables local modification of the chemical composition of metallic components within additive manufacturing processes. This new method represents an innovative process for localized grading of metallic materials in laser-based additive manufacturing. Smart-Alloying involves applying nanoparticulate alloying elements onto the surfaces...

Fibre-metal laminates (FML) are modern hybrid materials that combine metal and fibre-reinforced polymer layers. They are frequently used in aerospace and other high-performance applications due to their durability and fatigue resistance, improving structural integrity while simultaneously reducing weight. Compared to pure fibre reinforced plastics,...

The primary objective of this study is to clarify the fundamental question of whether, in principle, it is possible to dispense with a prior solution annealing process in favor of a direct aging heat treatment for specimens of maraging stainless steel grade X3NiCoMoTi18‐9‐5 (1.2709) produced by laser powder bed fusion (LPBF). The waiver of a soluti...

Due to its ease of processing, the stainless steel 316L is a widely used material for the laser powder bed fusion (PBF-LB/M) process. Compared to other additive manufacturing technologies PBF-LB/M has a lot of advantages such as design freedom and high resolution of details. However, PBF-LB/M also has some disadvantages, such as a reduced build-up...

The invention of Fibre Metal Laminate (FML) was a major breakthrough in the aerospace and the material world. The idea of combining monolithic sheets of metal with the fibre-reinforced polymer brought around multiple advantages over metallic materials offering much lower density and superior strength which paved its way towards lightweight structur...

Technical components should be produced sustainably and are subject to growing demands in terms of durability and reliability. To meet these expectations , the development of thermochemical processes is auspicious. Titanium alloys, which have a comparatively high gas solubility, allow temporary hydrogen charging, often called thermo-hydrogen treatm...

Technical components should be produced sustainably and are subject to growing demands in terms of durability and reliability, which makes the development of thermochemical processes auspicious. Titanium alloys feature comparatively high gas solubility and allow temporary hydrogen (H) charging, often called thermohydrogen treatment (THT). THT cause...

Technical components are subject to increasing demands regarding durability and reliability, which makes the development of thermochemical processes auspicious. Titanium alloys allow temporary hydrogen charging (thermo-hydrogen treatment: THT). The investigation presented evaluates the resulting mechanical properties, which arise from the realizati...

Detection of hidden damages in Fibre Metal Laminates (FML) is a challenge. Damage detection, classification, and localization is a part of the lower levels of Structural Health Monitoring (SHM) and is critical for damage diagnosis. SHM is an extremely useful tool for ensuring integrity and safety, detecting the evolution. Early damage detection and...

Parts of vehicles, such as landing gear components of aircrafts, are subject to growing demands in terms of sustainability via lightweight design and durability. To fulfill these requirements, the development of thermochemical processes is auspicious. Titanium alloys allow a heat treatment in hydrogen-containing atmosphere for temporary hydrogen al...

Due to the increasing use of the different composite materials in lightweight applications, such as in aerospace, it becomes crucial to understand the different damages occurring within them during life cycle and their possible inspection with different inspection techniques in different life cycle stages. A comprehensive classification of these da...

Despite a growing interest in additive manufacturing technologies, there is still a limited selection of suitable materials developed regarding the unique non-equilibrium cooling conditions. A highly promising alloy system for laser powder bed fusion (LPBF) is Al-Ce, which shows outstanding processability in recent studies. The medium strengths alr...

Technical components are subject to growing demands in terms of durability. Therefore, the development of thermochemical processes is auspicious. Titanium alloys allow for temporary hydrogen alloying, often called thermohydrogen treatment (THT). The investigation presented intends to realize a local microstructure adaptation of Ti-6Al-4V by means o...

Technical components are subject to growing demands in terms of durability. Therefore, the development of thermochemical processes is auspicious. Titanium (Ti) alloys allow temporary hydrogen alloying, often called thermohydrogen treatment (THT). The investigation presented intends to realize a local microstructure adaptation of Ti 6Al-4V via THT t...

Medium manganese steels can exhibit both high strength and ductility due to transformation-induced plasticity (TRIP), caused by metastable retained austenite, which in turn can be adjusted by intercritical annealing. This study addresses the laser additive processability and mechanical properties of the third-generation advanced high strength steel...

The mechanical properties of heat-treatable aluminium alloys are improved and adjusted by three different heat treatment steps, which include solution annealing, quenching, and aging. Due to metal-physical correlations, variations in heat treatment temperatures and times lead to different microstructural conditions with differences in the size and...

The majority of aluminum alloys used for laser powder bed fusion are based on the aluminum–silicon system, particularly alloys containing 7 to 12 wt.% silicon and less than 1 wt.% magnesium. Silicon has a beneficial influence on melt viscosity during casting and laser additive manufacturing and prevents the formation of cracks. This study focused o...

Thin metallic foils with a thickness below 50 µm are required for deep drawing of sub millimeter micro components. Commercial metallic foils for deep drawing are typically made of highly ductile materials such as pure aluminum, copper or stainless steel. Yet these materials are not suited for deep drawing of high strength micro components. Alloys w...

Cost-efficient and high-throughput material development processes and process chains are needed to meet the on-going demand for new metallic structural materials. Material development involves not only the processing of new material compositions, but also the material characterization. Hence, novel high-throughput screening methods are a promising...

Hot-deep drawing is an innovative processing technology to produce complex shaped sheet metal components with constant wall thickness from high-strength lightweight materials. For some aerospace and automotive applications oxidation resistance at medium to high temperatures is an important aspect. In terms of this titanium α-alloys are often used d...

The HPDC industry is changing, and E-mobility is one reason for this – power train components traditionally produced by HPDC are eliminated as the industry abolishes internal combustion engines (ICE). The casting industry reacts to this challenge by extending its product range towards structural automotive components - essentially large area/low th...

High-throughput screenings are established evaluation methods in the development of functional materials and pharmaceutical active ingredients. The transfer of this approach to the development of structural materials requires extensive adaptations. In addition to the investigation of new test procedures for the determination of material properties...

As part of a novel method for evolutionary material development, particle-oriented peening is used in this work to characterize 100Cr6 (AISI 52100) microparticles that were heat-treated by means of a differential scanning calorimeter (DSC). The plastic deformation of the samples in particle-oriented peening is correlated with the microstructural pr...

Rotary swaging is an incremental cold forming process that changes beneath the geometry also the microstructure and mechanical properties of the workpiece. Especially a new process design with Eccentric Flat Shaped Dies (EFSD) influences both the kind and amount of stress and plastic strain and consequently the material structure, and hence the mat...

The present text introduces a Special Section of Advanced Engineering Materials linked to the symposium Advanced Materials for Transport Applications organized by the authors within the framework of the EUROMAT 2017 conference. It introduces the contributions that make up this Special Section, and takes the fact that a majority of them is related t...

A novel method for evolutionary material development by using high-throughput processing is established. For the purpose of this high-throughput approach, spherical micro samples are used, which have to be characterized, up-scaled to macro level and valued. For the evaluation of the microstructural state of the micro samples and the associated micr...

Most heat treatment simulations of precipitation-hardenable aluminum alloys are incomplete or restricted to sub-steps of the process chain. In general, the studies addressing the heat treatment of aluminum components have only provided a qualitative guidance of heat treatment, which does not match the heat treatment that is necessary for specific p...

Material properties like yield stress and hardness change during forming. Metastable austenitic steels are characterized by an elevated work hardening potential due to strain-induced transformation of austenite into martensite especially by multi-stage processing. An application of a new rotary swaging process design with Eccentric Flat Shaped Dies...

Hot deep drawing (HDD) is an innovative promising compromise to reduce costs by saving production time and to reduce the expenses for surface treatment. Parts made by HDD provide a high accuracy and constant wall thickness suitable for automated industrial assembly. In this paper, the behavior of one near‐α titanium alloy, used to manufacture the c...

Additive manufacturing is considered a disruptive technology that is expected to revolutionize production technology and affect value chains on a global scale. The scope of accessible materials ranges from polymers to metals and ceramics as well as composites. The keynote will provide an overview of available manufacturing processes for the various...

Combining new processes for solidification, forming, and heat treatment on the micro as well as on the macro scale, the Collaborative Research Center “Farbige Zustände” develops a novel high‐throughput method for the research of new steel and aluminum alloys with advanced structural properties. These material scientific processes are accompanied by...

Monitoring of mechanical structures is a Big Data challenge concerning Structural Health Monitoring and Non-destructive Testing. The sensor data produced by common measuring techniques, e.g., guided wave propagation analysis, is characterized by a high dimensionality in the temporal domain, and moreover in the spatial domain using 2D scanning. The...

Today, micro components are used in various industrial sectors such as electronics engineering and medical applications. The final quality of such parts depends on each individual step of the production chain from the manufacturing of semi-finished parts to the post-processing. In this study, magnetron sputtering is used to manufacture thin (15-30...

Rotary swaging is an incremental cold forming process that changes beneath the geometry also the microstructure and mechanical properties of workpiece. Especially a new process design with Eccentric Flat Shaped Dies (EFSD) influences both the kind and amount of stress and plastic strain and consequently the material structure and hence the material...

Integral joints of aluminum with carbon fiber reinforced plastics (CFRPs) could help to reduce the weight of modern light weight constructions and also allow new constructions compared to the conventional riveting technology used nowadays. Aluminum–CFRP and aluminum–titanium joints frequently show galvanic corrosion if these materials are in electr...

The aim of this study was to find a strategy for obtaining the minimum possible resolution of selective laser melted parts of magnesium. Focus is laid on an enhanced process understanding, identification of strategies for resolution improvement and analyzing process limits. In order to reach these goals the influence of selected process parameters...

Mithilfe laserbasierter generativer Fertigungsverfahren (Laser Additive Manufacturing – LAM) ist es möglich, potentiell komplexe Bauteilgeometrien variantenreich herzustellen. Damit kann Gewicht eingespart werden und Funktionen sind integrierbar. In Kombination mit Automatisierungs- und innovativer Lasertechnik in der Schweiß- und Schneidapplikatio...

Because of their good properties, the γ‐TiAl based alloys are promising to replace the twice as dense yet established nickel‐based alloys e.g. in turbine blades and especially low pressure turbine blades in aircraft engines. The serial production of such parts made of the γ‐TiAl based alloys requires the development of a stable processing route. Ho...

In the foregoing years, micro components were frequently employed in various sectors such as the electronics and medical industry. In order to produce these components in large amounts and satisfying quality, the production processes have to be improved constantly. Heat treatment represents a critical step in the production chain of micro component...

The trend in the automotive and aircraft industry is moving towards customized designs by using compound structures, which provide an enlarged potential for weight and cost savings. Particularly, thermal joined lightweight structures made of aluminium alloys are characterized by moderate material and processing costs. However, the short and locally...

Verwendung von Leichtmetallen in Baugruppen und Verbundstrukturen zeigt ein großes Potential für Gewichts- und Kosteneinsparungen in der Luftfahrt- und Automobilindustrie. Insbesondere haben sich Aluminium und Aluminiumlegierungen als verhältnismäßig kostengünstige Werkstoffe durchgesetzt. Das thermische Fügen von Alumniumkomponenten führt jedoch z...

Combining different materials allows designing lightweight structures with tailor-made properties at the macroscopic as well as at the microscopic scale. In this context co-extrusion by lateral angular co-extrusion process (LACE) offers a great potential for advanced products by joining different light alloys, such as titanium and aluminum alloys....

Modern lightweight construction containing hybrid materials and structures allow the improvement of a wide range of density specific properties. In this regard, the great potential of structures consisting of carbon fibre reinforced plastics (CFRP) and aluminium (Al) is far from being exhausted. In order to exploit this potential, novel joint conce...

The combination of different light alloys enables lightweight solutions with tailor-made properties at the macroscopic global as well as at the microscopic scale. In this context co-extrusion by Equal Channel Angular Pressing (ECAP) offers a great potential for advanced profiled structures. While titanium alloys show particular high mechanical stre...

The combination of different light alloys enables lightweight solutions with tailor‐made properties at the macroscopic global as well as at the microscopic scale. In this context co‐extrusion by a lateral angular co‐extrusion (LACE) process offers a great potential for advanced profiled structures. While titanium alloys show particular high mechani...

The contribution serves as an introductory paper for a special issue of Materials & Design related to the Euromat 2013 conference held in Sevilla, Spain, from September 8th to 13th, 2013, and here specifically topic E2, Transportation and Mobility. It provides a brief overview of recent efforts at lightweighting with a special focus on the automoti...

Unlike thermoset fiber reinforced plastics (FRPs), thermoplastic FRPs provide excellent workability under elevated forming temperatures. Thus, complex shaped components made of thermoplastic FRPs become increasingly important for advanced lightweight applications, such as multi-material automotive bodies in white. To enable transition bonding betwe...

High strength aluminium alloys with improved stability at elevated temperatures for micro components, which are needed e.g. in the automotive or the micro electronics industry, require new alloys and advanced production processes regarding primary shaping, heat treatment and cold forming. Their development is part of the Collaborative Research Cent...

The combination of aluminum and titanium alloys allows for designing lightweight structures with tailor-made properties at the macroscopic global as well as at the microscopic scale. In this context both co-extrusion and friction welding offer a great potential for advanced solutions for products with material combinations of aluminum and titanium....

Components in hybrid design become more and more important in terms of their lightweight potential. In this context the demand for weight saving in aerospace structures leads to increasing numbers of applications of fiber reinforced plastics (FRP) for structural components. Besides FRP, metallic components are still parts of the primary structures....

Kurzfassung Die Ausscheidungshärtung von Aluminium-Legierungen erfolgt durch eine Wärmebehandlung, bei der sich insbesondere der integrierte Abschreckprozess entscheidend auf die resultierenden Festigkeits- und Verzugseigenschaften des Bauteils auswirkt. Zur Einstellung höchster Festigkeiten ist eine hohe Abschreckgeschwindigkeit nach dem Lösungsgl...

The objective of the AiF research project „Coupling of Process-, Microstructure- and Structural Simulation for evaluation of quasi-static strength of a laser beam welded hybrid joint (HyProMiS)“ (IGF 360 ZN) was the investigation of a welded joint between sheets made of aluminum EN AW 6082, steel DC04 as well as titan Ti6Al4V made through a heat co...

The continuous miniaturization of products needed e.g. in the automotive or the microelectronics sector requires process chains, which allow the manufacturing of microscopically small components in high quantities. The development of the required processes and technologies is the aim of the Collaborative Research Centre 747 “Micro Cold Forming” of...

Lightness, efficiency, durability and economic as well as ecological viability are key attributes required from materials today. In the transport industry, the performance needs are felt exceptionally strongly. This handbook and ready reference covers the use of structural materials throughout this industry, particularly for the road, air and rail...

Die hervorragenden spezifischen, mechanischen Eigenschaften von Faserverbundkunststoffen (FVK) führen, insbesondere bei der Substitution primärer Metallstrukturen, zu einem steigenden Bedarf im Flugzeugbau. Gleichzeitig erhöhen sich die Anforderungen konventionell eingesetzter Nietverbindungen, wie etwa dem Schließringbolzensystem. Notwendige Nietb...

A method and a device are provided for the thermomechanical treatment of seamless steel rings produced on radial-axial ring rolling machines, particularly rings of fine grain steel, heat-treatable steel, case hardened steel, or austenitic steel, preferably of steel tower flanges for wind turbine generators. The ring blank is inserted into the ring...

Being a pioneer in the field of modern transport applications aluminum has been developed to be the most important light alloy. This chapter shall give an overview of recent advances in material´s development that includes alloy design but also deployment of aluminum processing. The outstanding processing and in-service characteristics of aluminum...

During heat treatment of age hardenable aluminum alloys, the resulting mechanical properties and the distortion behavior can particularly be influenced by the quenching process. To achieve a required strength, a high efficient quenching rate after solution annealing is necessary. In order to avoid distortion, a homogeneous distribution of quenching...

The application of lightweight materials such as aluminium alloys, especially in systems stressed due to tribological contacts, calls for an additional modification of functional surfaces according to the loading conditions. Not least because of a modern generation of beam deflection techniques available, electron beam (EB) liquid phase surface tre...

Kurzfassung Um den gestiegenen Anforderungen an die Prozesse zur Fertigung von Kleinstbauteilen hinsichtlich Baugröße, Stückzahl, Kosten und Qualität gerecht zu werden, wurde der Sonderforschungsbereich 747 „Mikrokaltumformen“ der Deutschen Forschungsgemeinschaft an der Universität Bremen initiiert. Ein elementarer Prozessschritt in der Fertigung i...

During heat treatment of age hardenable aluminum alloys the resulting mechanical properties can be particularly influenced by the quenching process. To achieve the required strength, a high efficient cooling rate after solution annealing is necessary. In order to avoid distortion, a homogeneous distribution of quenching intensity should be realized...

Introduction Experimental research Results

Introduction FEM analysis and experimental research Results and Discussion Summary Acknowledgment

Introduction Experiments Results Modeling of hardness/strength distribution in the heat affected zone Conclusions Acknowledgement Acknowledgement

Introduction Experimental Results Conclusions Acknowledgement

Components in hybrid design become more and more important in terms of their lightweight potential. In this context, the demand for weight saving in aerospace industry leads to increase numbers of applications of fiber reinforced composites for primary structural components. In consequence, the use of FRP-metal compounds is necessary. In the contex...

The combination of different metallic materials enables the design of lightweight structures with tailor-made properties. In contrast to conventional joining methods, for example fusion welding, by co-extrusion no degradation occurs in the materials structure in the form of heat affected zones or pore formation. Therefore, co-extrusion exhibits an...

The combination of different metallic materials enables the design of lightweight structures with tailor-made properties at global as well as local scale and offers great potential for advanced solutions especially for the aircraft and automobile sector. However, after conventional fusion joining, e. g. after laser beam welding, heat affected zones...

Components in hybrid design become more and more important in terms of their lightweight potential. In this context the demand for weight saving in aerospace leads to increasing numbers of applications of fibre composites for primary structural components. In consequence the use of FRP-metal compounds is necessary. Within the investigations of the...

Materials Science and Engineering Technology Special Edition “Aluminium based compounds, composites and novel materials” Foreword Lightweight construction has become a universal requirement for all transportation systems. The availability of improved materials has enabled the continuous improvement of lightweight structures through enhanced spe...

The combination of different metallic materials, such as aluminium and steel or aluminium and titanium, by firmly bonding via laser beam welding enables the production of customised hybrid lightweight designs with enhanced properties. Both weld geometry and local material behaviour, which are responsible for the final load characteristics of the co...

Kurzfassung In der industriellen Praxis werden für moderne konstruktive Lösungen in beachtlichem Umfang Al-Werkstoffe genutzt. Die Umsetzung neuer Leichtbaulösungen wird jedoch aufgrund der Beanspruchungsbedingungen beschränkt, u. a. bzgl. Reibung/Verschleiß. Es sind Zusatzmaßnahmen zur beanspruchungsgerechten Modifikation der Randschichteigenschaf...

The combination of different metallic materials enables the design of lightweight structures with tailor-made properties. In contrast to conventional joining methods, for example fusion welding, by co-extrusion no degradation occurs in the materials structure in the form of heat affected zones or pore formation. Therefore, co-extrusion exhibits an...

Aluminium based materials are increasingly used for modern constructive solutions. However, the realization of modern lightweight construction solutions is strongly constricted regarding the limited load capacity, especially due to friction/wear. Thus, it is of large interest to modify the local properties close to the surface by means of additiona...

To face the increasing demands in the production of micro components concerning size scale, quantity, costs and quality new production processes must be established. At the University of Bremen the collaborative research centre 747 "Micro Cold Forming" funded by the German Research Foundation was founded to deal with the resulting challenges. An el...

During heat treatment of age hardenable aluminum alloys, the resulting mechanical properties are particularly influenced by the quenching process. To achieve the required strength, a high quenching rate after solution annealing is necessary, otherwise a homogeneous distribution of quenching intensity should be realized in order to avoid distortion....

Combinations of aluminum and titanium by firmly bonding via laser beam welding enable the production of customized hybrid designs with enhanced properties. A novel approach of coupling process, microstructure and mechanical simulation, considering the development of weld geometry and local material conditions, is intended to deliver a fast and reli...

This document provides the results of the process analysis of the co-extrusion of aluminum and titanium alloys. The compound consists of the slave material aluminum and the core material titanium. The investigation determines the influence of the parameters billet temperature, press ratio and core length on the process. The material combinations us...

The combination of aluminum and titanium enables the design of lightweight structures with tailor-made properties at global as well as local scale. In this context the co-extrusion process offers a great potential for advanced solutions for long products especially being applied in the aircraft and automobile sector. While titanium alloys show part...

The combination of different metallic materials enables the design of lightweight structures with tailor-made properties at global as well local scale and offers great potential for advanced solutions especially for the aircraft and automobile sector. Whereas titanium alloys show particular high mechanical strength and good corrosion resistance, al...

Modern lightweight structures containing hybrid materials allow an improvement of the weight-specific properties. In this regard, the great potential of FRP-Al (fibre reinforced plastic - aluminium) structures is far from being exhausted. As an alternative to bulky riveted joints the development of integral joint concepts with good corrosion resist...

The demand for increased efficiency of resources in industrial manufacturing processes requires continuous developments of materials and production processes. Aluminium components especially used in automotive applications meet the requirements of weight optimised and energy efficient solutions. In this context vacuum die casting enables the produc...

The continuous miniaturisation of products needed e.g. in the automotive or the micro electronic sector requires process chains which allow the manufacturing of microscopically small components in high quantities. The development of the required processes and technologies is the aim of the Collaborative Research Centre 747 “Micro Cold Forming” of t...

The economy of production processes is linked up to continuous developments of manufacturing processes. After the heat treatment in the process chain of Aluminium vacuum die casting components dimensional and shape changes occur, which require straightening operations. Influencing factors on the distortion are complex and mechanisms commonly unknow...

The economy of production processes is linked up to continuous developments of manufacturing processes. After the heat treatment in the process chain of Aluminium vacuum die casting components dimensional and shape changes occur, which require straightening operations. Influencing factors on the distortion are complex and mechanisms commonly unknow...

Laser beam welding (LBW) is an established serial process in manufacturing of parts for aircraft industries, which is characterised by the advantages of weight reduction and shortened process time compared to conventional riveting techniques. However distortions can occur after LBW. Depending on the intensity the distortions impair, e.g., assembly...

The thermo-mechanical treatment (TMT) offers great potential for energy and production cost savings by doing without a separate heat treatment. Nevertheless, the TMT technology has not been established in the field of the production of large seamless rolled rings yet. The reason for the low development level in the ring rolling field can be put dow...

Due to high cooling rates spray forming is an appropriate process to produce aluminum alloys with a high content of Mg2Si. Compared to common casting processes, a fine microstructure can be achieved yielding in improved mechanical properties. In this work, billets were spray formed from the two alloys AlMg15Si8Cu2 (22 mass-% Mg2Si) and AlMg20.5Si11...

Kurzfassung Das thermische Fügen in Kombination mit einer abschließenden Wärmebehandlung ist seit Jahren ein wichtiger Bestandteil bei der Herstellung von großen Strukturbauteilen im Flugzeugbau. Die nach der Wärmebehandlung auftretenden Konturabweichungen haben allerdings häufig aufwändige Rückformprozesse zur Folge, die die Wirtschaftlichkeit die...

Due to the rising demand for small high-performance products needed in wide sections of applications (for example automotive, micro electronics) the requirements for micro components concerning size scale (miniaturizing), quantity, costs and quality require new micro production processes to be developed. Dealing with the challenges of micro product...