Dynamics of melting processes in multiphase alloys

• Applicants: Dr. Guillaume Boussinot; Dr.-Ing. Stephanie Lippmann
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 530167777

The DYNAMELT project proposes an experimental and numerical study of the melting dynamics in multiphase, eutectic and peritectic alloys (multiphase melting). It aims at a first comprehensive investigation into pattern formation and microstructure selection during melting and melting/solidification (M/S) processes involving two solid phases. By combining up-to-date experimental and numerical methods, it takes advantage of winning methodological strategies in solidification. Fundamental and engineering-oriented aspects of interdisciplinary interest for nonlinear physics and materials science will be addressed. Main objectives are 1-to unveil elementary mechanisms during early stages of multiphase melting, 2-to analyse coupled-melting patterns in peritectic and eutectic alloys, and 3-to cast light on memory effects during M/S cycles. Melting of metallic alloys has been poorly studied experimentally and theoretically. Via novel industrial tools such as additive manufacturing, new motivation arose towards a better understanding of microstructure selection associated to M/S cycles on a basic level. Despite an apparent similarity, many asymmetries exist between melting and solidification: due to the low chemical diffusivity in solid phases, the solid alloy that melts contains frozen-in microstructures inherited from previous cooling stages. Partial melting and M/S cycles affect locally a previously built microstructure, and modify the material on a large scale. The project addresses transient and steady-state multiphase melting by means of temperature-gradient experiments, along with phase-field numerical simulations, in diffusion controlled conditions. The knowledge acquired from the study of preparatory and early-melting stages will serve as a basis for that of steady-state and M/S regimes. Pre-patterned microstructures will be melted with different processing parameters to investigate their influence on the melting dynamics, and their modifications upon re-solidification on a large scale. Specific aspects related to eutectic vs peritectic alloys, as well as challenging issues for numerical studies will be defined. This comprehensive approach will be achievable via well-targeted development from existing platforms. The methodology is based on a well-established expertise of the French- German consortium in the science of solidification and melting, with constant interaction between experiments and numerics, and mutual benefit. Bridgman-like experimental methods using model and metallic (Al-based) alloys in thin (INSP), and bulk samples held (FSU), or displaced (IJL) in a temperature gradient will be implemented. Phase-field simulations (ACCESS) on multiple length scales will be carried out in parallel. We shall learn from the complexity of initial-condition dependent phenomena, shedding light on the dynamics of multiphase melting. Proof-of-concept M/S based microstructure design is also expected, thus opening the way to knowledge-based strategies.

• DFG Programme: Research Grants
• International Connection: France
• Cooperation Partners: Professorin Dr. Sabine Bottin-Rousseau; Dr. Julien Zollinger