Study of ternary eutectic microstructures using 3D phase-field simulations and directional solidification experiments of Al-Ag-Cu

• Applicants: Professorin Dr. Britta Nestler; Professor Dr. Lorenz Ratke
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials
• Term: from 2010 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 191170049

• Final Report Year: 2018

Final Report Abstract

In this project, the directional solidification of the ternary eutectic system Al-Ag-Cu was studied in a collaboration between the German Aerospace Center (DLR) and the Karlsruhe Institute of Technology (KIT). The project partner in Cologne directionally solidified ternary eutectic Al-Ag-Cu alloys, which were investigated with two-dimensional cross sections and three-dimensional synchrotron tomography. Six characteristic patterns were found in the cross sections and were compared with statistical methods, like nearest neighbor statistics, triple point density, etc. In the 3D tomography data, several nucleation, combination, splitting and disappearing events, are detected. The 3D images provide first insights into the three-dimensional microstructure of a ternary eutectic systems. The project partner in Karlsruhe conducted phase-field simulations in close adjustment to the experiments. In the simulations, the minimum domain size for representative and statistical volume elements (RVE and SVE) are determined. The results of the microstructure data indicate the necessity of performing large-scale simulations. The computation of large-scale volume elements employing up to 86400 CPUs shows a good visual accordance with experiments. Furthermore spiral growth of two intertwinned phases, embedded in matrix phase is found as result of solid-solid anisotropy. This proves the assumption, that tilted growth in two dimension leads to spiral growth in three dimension, and confirms the indication of spiral growth in experiments. Also the microstructure rearrangement process due to dynamic velocity changes was investigated. Therefore a new graph based analysis method was developed and used for the simulation as well as the tomography experiments to investigate the 3D microstructure. From systematic variations of the composition in the ternary system, phase-field simulations were applied to establish a comprehensive morphology map incorporating regions of pattern transitions. In the line of ongoing efforts in the emerging discipline of integrated computational materials engineering, the same analysis tools were used to exploit experimental and simulated data. Using statistical methods like nearest neighbor statistics and principle component analysis (PCA) based on two-point correlations, we found an accordance between simulations and experiments. In continuation of the project achievements, samples of the studied alloy will be directional solidified on the international space station (ISS) as part of the project “Solidification along a Eutectic path in Ternary Alloys-2” (SETA-2) and the microstructure patterns will be compared with the experiments and simulations from this project.

Publications

• “New Metallographic Method for Estimation of Ordering and Lattice Parameter in Ternary Eutectic Systems”. In: Metallography, Microstructure and Analysis 2.3 (2013), pp. 140–147. issn: 21929262
  A. Dennstedt, L. Ratke, A. Choudhury, and B. Nestler
  
• “3D Synchrotron Imaging of a Directionally Solidified Ternary Eutectic”. In: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science 47.3 (2016), pp. 981–984. issn: 10735623
  A. Dennstedt, L. Helfen, P. Steinmetz, B. Nestler, and L. Ratke
  
• “Large-scale phase-field simulations of ternary eutectic microstructure evolution”. In: Computational Materials Science 117 (2016), pp. 205–214. issn: 09270256
  P. Steinmetz, J. Hötzer, M. Kellner, A. Dennstedt, and B. Nestler
  
• “Microstructures in a ternary eutectic alloy: Devising metrics based on neighbourhood relationships”. In: IOP Conference Series: Materials Science and Engineering 117.1 (2016). issn: 1757-8981, 1757-899X
  A. Dennstedt, A. Choudhury, L. Ratke, and B. Nestler
  
• “Phase-field simulations of spiral growth during directional ternary eutectic solidification”. In: Acta Materialia 106 (2016), pp. 249–259. issn: 13596454
  J. Hötzer, P. Steinmetz, M. Jainta, S. Schulz, M. Kellner, B. Nestler, A. Genau, A. Dennstedt, M. Bauer, H. Köstler, and U. Rüde
  
• “Phase-field study of the pattern formation in Al-Ag-Cu under the influence of the melt concentration”. In: Computational Materials Science 121 (2016), pp. 6–13. issn: 09270256
  P. Steinmetz, M. Kellner, J. Hötzer, A. Dennstedt, and B. Nestler
  
• “Influence of growth velocity variations on the pattern formation during the directional solidification of ternary eutectic Al-Ag-Cu”. In: Acta Materialia 136 (2017), pp. 335–346. issn: 13596454
  J. Hötzer, P. Steinmetz, A. Dennstedt, A. Genau, M. Kellner, I. Sargin, and B. Nestler
  
• “Graph-based investigation of three-dimensional microstructure rearrangement during ternary eutectic directional solidification of Al-Ag-Cu”. In: Journal of Crystal Growth 498 (2018), pp. 230–243. issn: 00220248
  P. Steinmetz, J. Hötzer, A. Dennstedt, C. Serr, B. Nestler, and A. Genau
  
• “Quantitative Comparison of Ternary Eutectic Phase-Field Simulations with Analytical 3D Jackson-Hunt Approaches”. In: Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science 49.1 (2018), pp. 213–224. issn: 10735615
  P. Steinmetz, M. Kellner, J. Hötzer, and B. Nestler
  
• “Study of pattern selection in 3D phasefield simulations during the directional solidification of ternary eutectic Al-Ag-Cu”. In: Computational Materials Science 148 (2018), pp. 131–140. issn: 09270256
  P. Steinmetz, J. Hötzer, M. Kellner, A. Genau, and B. Nestler