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Lightweight Materials

Research Field Lightweight Materials

Our research focuses on development, fabrication and characterization of advanced lightweight materials and components.

Mitarbeiterfoto Peter Randelzhofer

Peter Randelzhofer, M.Sc.

Mitarbeiterfoto Jonathan Wedler

Jonathan Wedler, M.Sc.

Mitarbeiterfoto David Himmler

David Himmler, M.Sc.

Mitarbeiterfoto Yan Zeng

Yan Zeng, M.Sc.

Mitarbeiterfoto Oleksandr Trudonoshyn

Oleksandr Trudonoshyn, M.Sc.

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Technical Reports

Ziel dieses Teilprojektes ist die Integration piezokeramischer Sensor-Aktor-Module in metallische Bauteile in einem Druckgießprozess. Den Lösungsweg für die schädigungsfreie Integration stellt die Ummantelung der einzugießenden Module mit einer von der Schmelze leicht durchdringbaren Drahtgewebestruktur dar. Hierbei minimiert die homogene Stützwirkung der Gewebestruktur die auf das Modul wirkenden lokalen Kräfte. Mit Hilfe von FE Simulationen wurden Prozessstrategien…

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The aim involved in designing metal matrix composite materials is to combine the desirable properties of metals and ceramics. The addition of high strength, high modulus refractory particles to a ductile metal matrix produces MMCs whose mechanical properties are excellent, such as high strength to weight ratio, high stiffness and good wear resistance. Due to these excellent attributes, MMCs are widely used in aerospace, automobiles, etc.
Among the variety of manufacturing processes available for particle reinforced aluminum materials, stir casting is generally accepted as a particularly promising approach as a result of its simplicity, flexibility, applicability to large quantity production and low costs of production. Though, in preparing particle reinforced aluminum materials by stir casting, we have to consider the following difficulties:
(1) How to achieve a uniform distribution of the reinforcement material.
(2) Promoting the wettability between the two main substances;
(3) Control chemical reactions between the reinforcement material and the matrix alloy.
A new high shear technology can be applied in producing particle reinforced aluminum materials. The aluminum melt is strongly sheared in the semi-liquid or liquid state. The high shear forces produced by a special designed impeller lead to very homogeneous dispersions of additives like particles. In addition, shearing has influence on the homogeneity of the melt and leads to finer grain structures. These effects are expected to be beneficial for the fabrication of metal matrix composites. Therefore, the particular focus of the project is to use shear device to introduce particles into an aluminum melt before die casting and the main aim is to evaluate the potential of the new high shear technology for conditioning of aluminum melts for pressure die casting.

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With Al-Mg-Si-Mn casting alloys with compositions inside of the pseudobinary section of the subsequent ternary phase diagram, the effect of Zn, Ti, Sc and Ag additions on the precepetation of nanoparticels in as-cast and heat-treated conditions as well as mechanical properties under different conditions (as-cast, solution treated, quenched andaged) will be studied. Despite of the established foundry practce of several Al-Mg-Si-Mn and Al-Zn-Mg casting alloys subjected to high pressure die casting only little research was done either on structure formation or strengthening mechanisms of these alloys and mechanical properties that can be achieved after additional alloying.

In frame of this project as cast conditions of AlMg5Si2Mn alloyed by Zn, Ti, Sc and Ag will be investigated paying attention to precipitates formed in solid solution matrix prior to heat treatment and changes of mechanical properties from as-cast state to age hardened.

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Die Auslegung von sicherheitsrelevanten Gussteilen im Leichtbau erfordert eine Berücksichtigung der inhomogenen Werkstoffeigenschaften bereits in der Konstruktionsphase, was aktuell in der Praxis noch nicht vollzogen ist. Durch Kopplung der Prozesssimulation mit der Lebensdauerberechnung sollen eine frühe Bewertung fertigungsbedingter Fehler im Hinblick auf die Schwingfestigkeit erreicht werden und konstruktive Maßnahmen zur optimierten Auslegung abgeleitet werden. Am Beispiel…

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Zellulare Materialien repräsentieren eine Materialklasse, deren strukturbedingte Eigenschaften mit abnehmender Zellgröße immer weiter an Potenzial gewinnen. Daher stellt die Reduzierung der Zellgröße werkstoffübergreifend ein wichtiges Entwicklungsziel dar. Weit fortgeschritten ist man bei Polymeren. Die Herstellung von mikro-zellularen Polymeren ist kommerzialisiert und man arbeitet bereits an der Realisierung nanozellularer Schäume. Ganz anders ist die Situation…

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Die Darstellung komplexer Geometrien lässt den konventionellen Druckguss schnell an Grenzen stoßen. Die Realisierung geometrisch einfacher Hinterschnitte ist nur durch den Einsatz mechanisch aufwendiger und wartungsintensiver  Schiebertechnologien möglich. Aus dem Sand- und Kokillenguss bekannte Sandkerne mit ihren organischen und anorganischen Bindersystemen halten den verfahrensspezifischen Drücken und Geschwindigkeiten nicht Stand und sind deshalb nicht für die…

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Complex 3-D carbon fibre preforms are to be infiltrated with aluminium in a high pressure die casting process. If our approach is successful, it will represent a major breakthrough compared to gas pressure infiltration, the state-of-the-art technology to manufacture fibre reinforced metal parts. Compared to the above mentioned technology, pressure die casting offers several advantages. The short cycle times characteristic for this process are not only of a substantial economic advantage, but also constrict the kinetically controlled deleterious reactions between the fibre-preforms and the aluminium matrix. Based on results of preliminary die casting experiments and numerical simulations of the infiltration process, an advanced mould design was realized in the past project phase further improving fibre preform preheating. In combination with advanced alloy compositions and fibre coatings developed by the project partners the main aims of the proposed continuation are to realize metal matrix composites (MMC) with improved transversal strength and ductility. A detailed understanding of the interface reactions is necessary to relate processing parameters, alloy and coating composition to the mechanical properties of the obtained MMC. In order to rationalise results, advanced microstructural investigations like SEM-FIB, high resolution TEM and numerical calculations of the infiltration process with Flow-3D and ABAQUS are envisaged.

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Integral foam molding (IFM) is an economical way to produce castings with integrated cellular structure, i.e. a solid skin and a foamed core. IFM is known for polymers since more than four decades and well established there in industrial production. Polymer integral foam parts are accepted as a material system with own properties which simplifies designs, reduces production costs and weight, and increases stiffness and overall strength. On the other hand, integral foam molding for metals is a new field of research. The development of metal based integral foam molding processes at WTM moves along analogous paths as that of polymers by transferring and adapting successful molding technologies for polymer integral foam to metals. Two molding techniques for metal integral foam are presented, a low and a high pressure process. During the low pressure integral foam molding process, the molten metal charged with blowing agent is injected into a permanent steel mold without completely filling it. In this case, the mold gets eventually filled by foam expansion. The strategy of the high pressure integral foam molding process HP-IFM is to initiate foaming by expansion of the mold cavity after it is completely filled with the mixture of the metal melt and the blowing agent.

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The objective is the integration of piezoceramic modules into metallic components by die casting. The main challenge is the control of the thermo-mechanical loads during mould filling and cooling. A new technology for a robust integration process suitable for mass production is explored. The experimental approach is always supported by the numerical simulation of the integration process.

SFB/TR 39 (http://www.pt-piesa.tu-chemnitz.de/P_3/index.php)

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Production of hollow parts and complex undercuts in high pressure die casting. In high pressure die casting (HPDC) undercuts are only producible by using complex and thus high-maintenance sliders. Until now it is not possible to produce hollow cast parts by means of this technology. Known sand cores from sand- and low pressure die casting with their organic and inorganic binder systems are not suitable for the application in HPDC since they cannot cope with the process specific parameters. The use of lost cores made from salt constitutes a solution. After casting, the core can be removed completely from the part with a pressure water jet making sand-free castings and the integration of complex undercuts possible in HPDC.

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The development of Aluminum alloys mainly tends to increase the strength without worsening the ductility. Beside strength an increase in stiffness is also sought. In contrast to strength with Aluminium casting alloys the stiffness can be influenced by alloying to a very small extent only. A substantial increase in stiffness is possible by metal matrix composits. But poor wettability between the metal matrix and the ceramic particels and big differences in the thermal expansion lead to poor mechanical properties. One possible approach to solve these problems is using intermetallics based on Aluminium as reinforcement. These phases have a low density and a good wettability with the Aluminium matrix. Moreover, these phases can be produced by an in-situ reaction in the aluminum melt. The volume fraction of the reinforcing phase increases with this reaction. A special stirring technique ensures that the reinforcing phase is finely divided and the matrix solidifies fine-grained.

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Despite of the established foundry practice of several Al-Mg-Si-Mn and Al-Zn-Mg casting alloys subjected to high pressure die casting, only little research was done either on structure formation or strengthening mechanisms of these alloys and mechanical properties that can be achieved after additional alloying.

As cast conditions of AlMg5Si2Mn alloyed by Zn, Ti, Sc and Ag will be investigated paying attention to precipitates formed in solid solution matrix prior to heat treatment and changes of mechanical properties from as-cast state to age hardened state.

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The design of safety-relevant castings in lightweight constructions requires consideration of the inhomogeneous material properties already in the design phase. Usually global component properties are used for the dimensioning of constructions, for example the volume fraction of the porosity with regard to the vibration resistance. It is striven for to differentiate the influence of microstructure and casting defects on mechanical properties depending on type, size, morphology and location of the defects. The results, fed into lifetime calculation and coupled with process simulation, should allow an early assessment of manufacturing-related errors to derive constructive improvements.

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