Confined spinodal fluctuations at crystal defects evidenced in Fe-Mn alloys
In this ongoing project, we investigate spinodal fluctuations at crystal defects such as grain boundaries and dislocations in Fe-Mn alloys using atom probe tomography, electron microscopy and thermodynamic modeling [1,2].
Analysis and design of materials and fluids requires understanding of the fundamental relationships between structure, composition and properties. Dislocations and grain boundaries influence microstructure evolution through the enhancement of diffusion and by facilitating heterogeneous nucleation, where atoms must overcome a potential barrier to enable the early stage of formation of a phase. Adsorption and spinodal decomposition are known precursor states to nucleation and phase-transition, however nucleation remains the less well understood step in the complete thermodynamic sequence that shapes a microstructure. Here, we report near-atomic-scale observations of a phase transition mechanism which consists of solute adsorption to crystalline defects followed by linear and planar spinodal fluctuations in a Fe-Mn model alloy. These fluctuations provide a pathway for austenite nucleation due to the higher driving force for phase transition in the solute-rich regions. Our observations are supported by thermodynamics calculations, which predict the possibility of spinodal decomposition due to magnetic ordering.
International researcher team presents a novel microstructure design strategy for lean medium-manganese steels with optimized properties in the journal Science
This project deals with the phase quantification by nanoindentation and electron back scattered diffraction (EBSD), as well as a detailed analysis of the micromechanical compression behaviour, to understand deformation processes within an industrial produced complex bainitic microstructure.
Within this project, we will use a green laser beam source based selective melting to fabricate full dense copper architectures. The focus will be on identifying the process parameter-microstructure-mechanical property relationships in 3-dimensional copper lattice architectures, under both quasi-static and dynamic loading conditions.
Within this project, we will use an infra-red laser beam source based selective powder melting to fabricate copper alloy (CuCrZr) architectures. The focus will be on identifying the process parameter-microstructure-mechanical property relationships in 3-dimensional CuCrZr alloy lattice architectures, under both quasi-static and dynamic loading…
The fracture toughness of AuXSnY intermetallic compounds is measured as it is crucial for the reliability of electronic chips in industrial applications.
The focus lies on the investigation of the fracture properties of materials down to the individual microstructural length scale, with special attention on grain/phase boundaries or material interfaces, while considering the role of crystallography, chemistry and non-ambient conditions such as high temperatures and cryogenic conditions on fracture.
In this project we work on correlative atomic structural and compositional investigations on Co and CoNi-based superalloys as a part of SFB/Transregio 103 project “Superalloy Single Crystals”. The task is to image the boron segregation at grain boundaries in the Co-9Al-9W-0.005B alloy.