Theoretical and phase field modeling of chemical segregation and microstructure formation in rapid solidification of nickel-based superalloys

• Applicant: Professor Dr. Peter Galenko
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 448319030

In description of mechanisms of pattern formation in rapidly solidified materials, theoretical predictions of the formation of metastable phases are based on models that include deviations from local thermodynamic equilibrium. Such models are expected to provide the necessary understanding of the mechanisms of microstructure formation to develop advanced processing technologies. In the present project proposal we plan to model microsegregation and primary crystal microstructure upon rapid solidification of Ni-based superalloys. This type of alloys have been chosen due to their exceptional mechanical properties at high temperatures. Rapid solidification will be modeled consistently with the experimental data obtained on microstructure and microsegregation of Inconel 718 obtained by Chinese colleagues. With this concept, we plan to (i) link Gibbs free energies from CALPHAD and mesoscopic models; (ii) make estimations of relaxation times (for diffusion fluxes, gradient flows and phase field) and of kinetic parameters of sharp interface and diffuse interface models (interface mobility, diffusion coefficients and growth kinetics coefficients); (iii) develop of gradient stable computational schemes and algorithms for the prediction of microstructures formed by rapid solidification; (iv) provide special tests including comparison with data of atomistic simulations, experiments on directional solidification and in-situ observations in transmission electron microscope; (v) carry out theoretical modeling of non-equilibrium effects (solute trapping and degeneration of solute drag) and convective flow under rapid solidification. As a result, theoretical modeling using sharp interface and diffuse interface (phase field) models of crystal growth kinetics and microstructure formation in rapid solidification of Ni-based superalloys will be made (by German partners) in parallel and in comparison with in-situ observations of crystal growth kinetics and microstructure formation in rapid solidification of Ni-based superalloys (that will be given by Chinese partners). Due to close collaboration of German and Chinese groups, currently open problems on microstructure formation and elemental microsegregation of superalloys on the mesoscopic length scales are expected to be solved enabling the development of a new generation of Ni-based superalloys with superior mechanical properties.

• DFG Programme: Research Grants
• International Connection: China
• Partner Organisation: National Natural Science Foundation of China
• Cooperation Partner: Professor Dr. Jianrong Gao