Chair of

High Temperature Materials

As part of the scientific and technical collaboration, the aim is to produce high-performance metal-matrix composites based on multi-component materials for high-temperature applications. In particular, the production of multicomponent materials is simplified by a combination of classic powder metallurgy and spark plasma sintering processes and should guarantee significantly improved (mechanical) properties. This method makes it possible to implement a material design tailored to specific applications and at the same time represents a scientific and technological challenge. In addition, the addition of ceramic particles makes it possible to increase the strength of the alloys. The technology to be tested could be applied on an industrial scale in the future.
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Metallic materials for applications as structural materials, e.g. in corrosive environments at different temperatures, must have a wide range of properties. By adding alloying elements, the properties can be influenced over a wide range. For example, the strength of molybdenum materials can be significantly increased by adding even small amounts of silicon. Other properties, such as tribological abrasion, the oxidation or corrosion rate and cyclic strength, are also heavily dependent on the selection, concentration and combination of alloying elements. In addition, the heat treatment condition of the alloys plays a major role in adjusting the range of properties to suit the application. For materials in the medical sector, e.g. implant materials, properties under varying stress conditions (cyclic loading) also play a decisive role. The aim of this project is to modify materials in such a way that hardness and wear resistance are increased and static and cyclic stress resistance is improved without reducing oxidation and corrosion resistance. The microstructure-property relationships are specifically influenced in order to create optimum conditions for the subsequent application.
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The overarching aim of the ME-MAT project is to establish a network between cooperation partners from Germany, Poland, Bulgaria and Hungary.
The scientific focus is on adapting powder production for additive manufacturing processes. As the envisaged multiphase material from the group of refractory metals has an extremely high melting temperature and is also very reactive under environmental conditions, challenging research questions arise.
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The demand for new high temperature alloys increases due to economic reasons and stricter climate protection and resource conservation requirements. For applications in the field of energy conversion, new Mo-Si-B materials are in the focus of current research. There is a specific interest in alloys with a continuous Mo matrix phase and silicide particles, which provide an acceptable fracture toughness and high creep resistance at the same time.
A drawback of potential applications of Mo-Si-B alloys, e.g. as rotating turbine blades, is the density of > 9 g/cm³. Therefore, this project aims into a density reduction of this alloy type, meeting values of < 8 g/cm³. This is challenging because significant losses in the fracture toughness and the creep resistance should be avoided.

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Subproject: Microstructural damage of coated AlSi materials under mechanical and thermal stress

Editing: Dipl.-Ing. Philipp G. Thiem     
  
New intermetallic coating systems on AlSi substrates are being investigated. The coated materials are subjected to both static and cyclic loads in order to investigate the effects of the alloy composition, the microstructure and the coating thickness on crack formation and crack propagation in the application-relevant temperature range. Material parameters, e.g. the modulus of elasticity, and other parameters such as the adhesive strength of the coating are to be included in the modeling of the damage mechanisms in this material composite.  

Subproject: Crack initiation and crack propagation in multiphase high-temperature materials

Editing: M.Sc. Julia Becker    

Multiphase high-temperature materials are investigated with regard to crack initiation in the individual phases, crack propagation and their fracture toughness. Initial experiments on crack initiation and crack propagation were carried out on Mo-Si-B alloys produced by powder metallurgy using the indentation fracture mechanics method. The findings are to be transferred to directionally solidified multiphase molybdenum materials.

Collaboration in other sub-projects:
* Experimental Investigations and Numerical Simulations of Lamellar Cu-Ag Composites

Editing: M. Sc. Srihari Dodla
Supervision: Prof. A. Bertram, Prof. M. Krüger

* Crystal Viscoplasticity Based Simulation of Ti-Al Alloy under High-Temperature Conditions

Editing: M. Sc. Helal Chowdhury
Supervision: Prof. K. Naumenko, Prof. H. Altenbach, Prof. M. Krüger
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