Numerical and experimental study on the fragmentation of dendrites in the mushy zone of binary metal alloys

• Applicants: Professorin Dr. Britta Nestler; Professor Dr. Markus Rettenmayr (†)
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2008 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 62728097

Fragmentation of dendrites is a technologically important phenomenon occurring in the mushy zone of a solidifying melt, mainly during late stages of solidification. Fragmentation has a crucial impact on the grain structure of different cast parts, which in turn determines the properties of the solidified material. The goal of the proposed research project is to numerically and experimentally investigate the complex interaction of the parameters (temperature field, concentration field and interfacial energy) involved in the dendrite fragmentation, and to quantify fragmentation by detailed modelling for the first time. A fast 2-dimensional “CA stabilised diffusion model” for dendritic growth will be extended to 3 dimensions. The interaction of concentration field and capillarity will be analysed to investigate the conditions and mechanisms of fragmentation. Multiscale 2D and 3D phase-field simulations of dendritic fragmentation processes for different process conditions and under the influence of fluid flow will be performed for validation and comparison with the CA computations. In addition, experimental investigations will also be carried out for comparison and to validate the numerical model. Equiaxed microstructures with fragmented dendrites will be generated in a gradient furnace using Al-Cu alloys. A ”data base” of combinations of parameters that lead to fragmentation under diffusive conditions will be established.

• DFG Programme: Research Grants