CD Laboratory for Early Stages of Precipitation

A physical process known as precipitation reaction in high-performance materials is being investigated. These reactions involve the crystallisation of dissolved substances in the solid material state, which play a decisive role in shaping key material properties.

If high-performance materials - such as nickel-based alloys, tool steels or so-called refractory metals (metals with a very high melting point) - are to be further optimised, their microstructures must be better understood. Microstructures are the arrangements of solid material components that do not react chemically with each other. In addition to the size of crystal grains and the totality of their interfaces, the properties of the material are influenced in particular by precipitates in this microstructure.

Research is particularly concerned with the development and improvement of examination methods for analysing these tiny structural components. Since the temporal sequence of precipitate formation during material processing cannot be analysed directly in the material, the continuous description must be replaced by detailed analysis of individual, punctual precipitate states. For this purpose, methods are being developed that allow a spatial resolution in the nanometre range and the analysis of the chemical composition of tiny precipitates. Transmission electron microscopy and the so-called atom probe are particularly suitable for this purpose; both are direct methods for analysing material structures. On the other hand, small-angle scattering and differential thermal analysis work indirectly, allowing conclusions to be drawn about the characteristics of the precipitates through the interaction of neutron or X-ray radiation.

All of the methods mentioned are being further developed, optimised and applied in a complementary manner. Fluctuations in the material composition, size and shape of the precipitates and their particle density are characterised in detail. Based on this, the relationships between the microstructure, i.e. the microstructure, the precipitates and the mechanical properties of a material are investigated. At the same time, the knowledge gained is used to further develop an increasingly important tool in materials science: the computer simulation of processes in materials production and processing. Therefore, a key objective of the research is also the development of software programmes that enable the simulation of precipitation processes.