Titanium alloys are widely used in industry due to their superior properties, such as high strength, corrosion resistance, biological compatibility. Here, we study the substitution energy of Nb in Ti and reveal important consequences for the stability of various stable and metastable phases.
Ab initio methods based on DFT are now routinely used to investigate T=0 K properties. In contrast, finite temperature DFT studies are rare and, in particular, limited to approximations such as the quasiharmonic model. In the present study, we investigate the influence of anharmonic excitations—which correspond to phonon-phonon interactions beyond the simple quasiharmonic picture—on the thermodynamics of Ti and TiNb alloys.
Our joint CM-MU project is aimed at theoretical identification of fundamental materials design limits in bcc Mg-Li alloys for ultra light-weight applications.
Inter-departmental theoretical and experimental study of low-concentration Yadditions in Mg that are enhancing its room-temperature ductility. The theoretical part consists in (i) quantum mechanical calculations of Mg-Y crystals and (i) coarse-graining of the results within the Axial Next Nearest Neighbour Ising (ANNNI) model.
Phase stabilities of multicomponent material systems are best simulated with CALPHAD. The underlying databases are mainly obtained from calorimetric measurements, but suffer often from the fact that for certain phases an experimental approach is not feasible or not conclusive. Here, ab initio calculations emerge as an alternative, which is carefully investigated for the Al-Mg-Si-Cu system within this project.
The energetics and dynamics of hydrogen in metals is a central topic of metal research. Due to its connection to hydrogen embrittlement and hydrogen storage it is highly interesting to scientists as well as engineers. In this study, various materials have been examined in order to identify chemical trends for the solubility and mobility of hydrogen.
Due to their interaction with interstitial elements, the concentration of vacancies in metals can increase by several orders of magnitude. The so called superabundant vacancy formation is in particular discussed in the context of hydrogen in metals. Our ab initio calculations prove that such a mechanism can also be relevant for austenitic steels.
Electrochemical dealloying of metallic alloys can be regarded as a detrimental (wet) corrosion process related e.g. to stress corrosion cracking. Noble metal alloys like Ag-Au or Cu-Au constitute model systems and are investigated to gain basic understanding of corrosion processes.
Joint inter-departmental research in a close collaboration with the department of Prof. Raabe is an example of a theory-guided materials design of novel mechanically bio-inspired materials for human implants.
Hydrogen induced embrittlement of metals is one of the long standing unresolved problems in Materials Science. A hierarchical multiscale approach is used to investigate the underlying atomistic mechanisms.
The fascinating material properties of magnetic shape memory alloys are investigated by exploring their free energy surfaces. The aim is an atomistic knowledge about the stable crystal structures and the low energy transformation paths.
The aim of this project is the development of a complete first-principles based methodology to study the magneto-caloric effect (MCE) close to the technologically and scientifically relevant regime of first order magneto-structural transitions.
Samarium-cobalt intermetallic compounds contain with SmCo7 a phase, which is due to its metastability and complexity not very well characterized yet. Our ab initio based analysis helped to resolve its structure and provides valuable insights into the thermodynamic properties of this phase.
We study steady-state solidification along the liquid-liquid interface in a syntectic system by means of a boundary-integral technique. We study the case of small asymmetry of the pattern and extract from the results the scaling relations in terms of the undercooling and the asymmetry parameter. We also investigate monotectic solidification using the phase-field method.