Grain boundaries strongly influence the mechanical behavior and other materials properties. At high homologous temperature, grain boundaries can display pronounced disorder, manifested in the most extreme case by the formation of nanometer-scale intergranular films with liquid-like properties. The formation of those films below the bulk melting point, typically referred to as grain boundary premelting, can dramatically reduce shear resistance and lead to catastrophic materials failure.
High-Mn-steels are excellent candidates for the next generation of high-strength materials. In such steels the prevailing plasticity mechanism is determined by stacking fault energy. In this study, we aim to develop a generalized first-principles framework that allows temperature- and composition-dependent atomic-scale description of the stacking fault properties, necessary to explore chemical trends, to deliver parameters for mesoscale models, and to identify new routes to optimize high-Mn-steels.
The mechanical properties of high-Mn steels sensitively depend on the dominating type of deformation mechanism, which is known to correlate with the value of the intrinsic stacking fault (SF) energy. In this project we use combination of first-principles calculations and kinetic Monte Carlo simulations to quantitatively study the segregation and anti-segregation processes of alloying elements at the stacking faults, thus explaining how chemical alloying influences mechanical properties of high-Mn steels on atomic level.
Nanowires have a length to diameter ratio of about 1000 and a thickness of some nanometers and exhibit interesting electronic properties. Often, they grow defect-free in a catalytic reaction from a substrate, but recently interesting patterns have been observed in situations, where the wires grow in a controlled way with a screw dislocation inside the trunk. In this project we investigate the dislocation motion and morphology of the nanowire, as well as nanowire stability.
The migration of grain boundaries in polycrystalline materials plays a crucial role in the evolution of microstructure in processing and application. A clear picture of how grain boundaries move is necessary for a full understanding of the mechanical properties of materials and will help enable the design of new materials to meet current technological challenges. Our research uses classical molecular dynamics simulations ...