Nucleation in metals and metal alloys – An atomistic view

• Applicant: Privatdozentin Dr. Jutta Rogal
• Subject Area: Theoretical Condensed Matter Physics ; Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: from 2014 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 262052203

Metals and metal alloys form the basis for a wide range of complex materials classes that have important applications in the energy and transportation sector. To advance the development of new materials for special purpose applications it becomes essential to understand macroscopic materials properties based on insight gained on the atomistic level. Obtaining knowledge about atomistic processes during solidification and melting constitutes one of the basic steps to improve our understanding of the materials behaviour during processing and under service conditions. In solid-liquid phase transformations the selectivity of specific polymorphs and the development of the microstructure are determined to a large extend already during the initial stages of nucleation. Both experimentally and theoretically an atomistic description of nucleation processes is very challenging but crucial to understand the atomistic mechanisms that take place during nucleation and growth. In this study we employ advanced simulation techniques, in particular transition path sampling, to investigate nucleation processes during solidification and melting. As a material system we focus on nickel and nickel alloys that constitute key components in several technological relevant materials.Based on the results obtained during the first funding period we have identified three primary objectives for the current research project: the insight gained on nucleation processes in pure metals (Ni) is extended to binary alloys (Ni-Al) with a particular focus on how the chemical order influences the nucleation mechanisms and what kind of order parameters are needed to capture this behaviour. A second aspect is the investigation of how defects affect the pre-ordering in the liquid to promote the growth of particular polymorphs. Together with certain environmental conditions (temperature, pressure) such nucleation seeds might be used to trigger the formation of specific crystal structures. A third aspect is the extension to heterogeneous nucleation during melting, in particular at superheated grain boundaries, providing a direct comparison between atomistic processes during solidification and melting.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Ralf Drautz