Fast, physically - based algorithms for modelling the heat treatment of refractory composites and material compounds in relation to their properties

• Applicants: Professor Dr.-Ing. Ulrich Prahl; Privatdozent Dr.-Ing. Matthias Schmidtchen
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Glass, Ceramics and Derived Composites
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 416817512

The research group is developing a metal-ceramic composite material made of aluminium oxide and metallic niobium or tantalum for refractory applications.This material is characterised by its electrical conductivity, which makes it interesting for use in refractory functional components.The material is manufactured by sintering.The sintering of powders is mainly caused by diffusion processes, which are driven by the energy gain due to the reduction of the surface area and the formation of grain boundaries. The sintering progress is thus largely determined by the geometry of the powder particles used. Previous models of sintering usually considered particles of equivalent spherical or circular shape, which greatly simplifies the modelling, but neglects significant properties of the real powder.In the previous project phase, a sintering model was developed that is able to describe the sintering behaviour of non-ideal particle geometries.The influence of the particle geometry on the sintering behaviour was investigated and described.By statistically describing the shape of individual particles, it was possible to characterise powders in terms of particle morphology.These data could be used as input into the developed sintering model, so that the particle morphology could be taken into account in the sintering simulation.In the funding period applied for here, the aim is to further develop the sintering model with regard to additional effects in the contact of several particles, which have not been taken into account so far, and with regard to the consideration of the composition of the investigated material from coarse as well as fine grain fractions by treating both fractions separately in the simulation.Furthermore, an experimental validation of the model is to be carried out.In TP3 of the previous period, the mechanical behaviour of the composite material was investigated in high-temperature crush tests. This revealed a high plasticity of the material, which is attributed to pore closure made possible by the plasticity of the metal phase. The material behaviour found in this way is to be reproduced in the project applied for here by means of a crystal plastic simulation (DAMASK) and thus better understood.

• DFG Programme: Research Units
• Subproject of: FOR 3010: Multifunctional, coarse grain Refractory Composite Materials for Key-Components in High temperature applications