The NFDI-MatWerk consortium will focus on the research area Materials Science & Materials Engineering 405&406 of the DFG subject classification system. The digital representation of materials and their relevant process and load parameters is the central challenge. The digital transformation in materials science and materials engineering is the way there and at the same time part of the vision of the NFDI-MatWerk.
Experimental and stochastic investigations of the influence of the inclusions on the fatigue life
The objectives of this subproject of SFB920 are the determination of the largest existing, i.e. fracture-initiating, non-metallic inclusion that has not been filtered, and the determination of the dependence of the fatigue life distribution in the case of fatigue loading in the range of long service lives on the inclusion distribution. In order to be able to investigate the failure of internal inclusions in the VHCF range more specifically, specimens with modified surface properties (residual compressive stresses) and under tensile mean stresses are tested. Microstructural characterizations of the inclusions in the cast as well as in the failed state serve to elucidate the formation and damage mechanisms of inclusion agglomerates. The development of a three-dimensional thermo-mechanical simulation model that can predict the heat generation during fatigue allows to conclude about the spatial distribution of the heat source(s) inside the samples, so that further conclusions about the crack initiation and growth behavior in the VHCF range can be expected from the dissipated energy.
Tailored agglomeration to increase separation efficiency
This subproject of SFB920 investigates the mechanisms of agglomeration and heterocoagulation of model inclusion particles in a water-based ambient temperature model. The focus is on the kinetics of continuous heterocoagulation and on the micro-processes during the contact between bubble and particle. Furthermore, for the first time flotation of inclusions is considered and quantified as a cleaning mechanism. The insight in the fundamental mechanical properties of the agglomerates will be generated with a molecular-dynamic multi-scale approach both in the model system and in the real system, allowing the validation of the results of the model system
Control of the microstructure of thin multilayer systems by ultrashort pulsed laser irradiation - process understanding by complementary in situ and ex situ characterizations and multiscale simulations
The aim of this DFG research grant is to contribute to the understanding of laser-induced changes in the microstructure of thin metallic films and to the description of the effect of microstructure on the materials characteristics, which are relevant for the laser processes, e.g., absorption of the laser beam, electron-phonon coupling, heat transfer, etc. This aim should be achieved by combining in situ (ultrafast ellipsometry and reflectometry during the laser irradiation) and ex situ experiments (scanning and transmission electron microscopy, X-ray and electron spectroscopy) with simulations using mesoscopic (hydrodynamics) and microscopic (molecular dynamics) approaches. The evaluation of the electron micrographs will be supported by a multimodal analysis based on deep learning. The information obtained from the molecular dynamic simulations will complement the ex situ microstructure studies by providing, e.g., the atomic positions for the in situ microstructure analyses during the laser irradiation.The materials proposed for this study are single layers (Cr, Mo, Ti, Fe) and bilayers (Au/Cr, Mo/Ti, Au/Fe) consisting of unary metallic phases with different melting points, different sequences of high-temperature and high-pressure phases, and with different mutual solubilities and diffusivities in the respective binary system. Experimentally observed phase transitions and concentration profiles will be used as “sensors” for the temperatures and pressures induced by the laser irradiation. The effect of the microstructure on the laser process will be studied in samples having different grain size and preferred orientation of crystallites in the original state.