Influence of growth velocity variations on the pattern formation during the directional solidification of ternary eutectic Al-Ag-Cu

Hoetzer, Johannes
Steinmetz, Philipp
Dennstedt, Anne
Genau, Amber
Kellner, Michael
Sargın, Irmak
Nestler, Britta
In order to control the evolving microstructure in complex eutectics and other multi-phase systems, it is important to understand the adjustment mechanisms and the parameters that determine pattern evolution. Here, a combined experimental and simulation approach is taken to investigate the response of a three-phase eutectic system to changes in solidification velocity. Using Al-Ag-Cu as a model system, large scale three-dimensional phase-field simulations are compared to directionally solidified samples containing both, velocity increases and decreases. The experimental results are obtained by synchrotron tomography for detailed consideration of the microstructure directly before and after a targeted velocity change and by traditional SEM analysis of sample cross sections to capture effects over longer length scales. In addition to qualitative analysis of the images, the microstructures are statistically assessed using phase fractions, shape factor and nearest neighbor statistics. Both, simulation and experiment show an immediate change in phase fraction as a result of a change in growth velocity. Adjustment of the microstructural pattern occurs more slowly over a relatively long length scale, due to splitting, merging and overgrowing events. Novel quantification techniques emphasize that ternary eutectic phase arrangements are complex and continuously evolving structures which, even under ideal conditions, do not reach steady state growth as quickly as previously believed.


Effects of anisotropic surface drift diffusion on the strained heteroepitaxial nanoislands subjected to electromigration stressing
Oğurtanı, Tarık; Celik, Aytac; ÖREN, ERSİN EMRE (2022-02-01)
A systematic study based on self-consistent dynamical simulations is presented for the morphological evolutionary behavior of an isolated thin Ge/Si nanoisland (quantum dot) on a rigid substrate exposed to electromigration forces. This morphological evolution is basically induced by the anisotropic surface drift diffusion, driven by the capillary forces, the lattice mismatch stresses, and the wetting potential. In this study, we have mainly focused on the size and shape development kinetics of quantum dots,...
Evolution of Self-Organized Task Specialization in Robot Swarms
Ferrante, Eliseo; Turgut, Ali Emre; Duenez-Guzman, Edgar; Dorigo, Marco; Wenseleers, Tom (Public Library of Science (PLoS), 2015-08-01)
Division of labor is ubiquitous in biological systems, as evidenced by various forms of complex task specialization observed in both animal societies and multicellular organisms. Although clearly adaptive, the way in which division of labor first evolved remains enigmatic, as it requires the simultaneous co-occurrence of several complex traits to achieve the required degree of coordination. Recently, evolutionary swarm robotics has emerged as an excellent test bed to study the evolution of coordinated group...
Impact of Number of Interactions, Different Interaction Patterns, and Human Inconsistencies on Some Hybrid Evolutionary Multiobjective Optimization Algorithms
Marquis, Jon; Gel, Esma S.; Fowler, John W.; Koeksalan, Murat; Korhonen, Pekka; Wallenius, Jyrki (2015-10-01)
We investigate the impact of the number of human-computer interactions, different interaction patterns, and human inconsistencies in decision maker responses on the convergence of an interactive, evolutionary multiobjective algorithm recently developed by the authors. In our context an interaction means choosing the best and worst solutions among a sample of six solutions. By interaction patterns we refer to whether preference questioning is more front-, center-, rear-, or edge-loaded. As test problems we u...
Effect of Seismic Source Model Parameters on the Probabilistic Seismic-Hazard Assessment Results: A Case Study for the North Anatolian Fault Zone
Gülerce, Zeynep (2015-10-01)
The inputs to the probabilistic seismic-hazard analysis (PSHA) contain large uncertainties regarding the seismic source model parameters; therefore, results may vary significantly due to subjective judgment and interpretation of the limited data. The objective of this study is to show the effect of seismic source models on the hazard results by quantifying the differences in the design ground motions for different hazard levels at different locations around the North Anatolian fault. Analysis showed the var...
Stochastic Analysis of Human Postural Sway
Yaradanakul, Naci; Gürses, Senih; Department of Engineering Sciences (2022-9-2)
"The decisive step in the transition from ape to man", in other words, inherently unstable dynamics of human erect posture, is investigated throughout the thesis considering the random features with a spatiotemporal perspective employing stochastic dynamical system theory and statistical mechanics. During the investigation, mechanistic reasoning and control theory is not mentioned, but the complex dynamical output of four basic sensors somatosensory, vestibular, visual and proprioceptive, physicochemical ac...
Citation Formats
J. Hoetzer et al., “Influence of growth velocity variations on the pattern formation during the directional solidification of ternary eutectic Al-Ag-Cu,” ACTA MATERIALIA, vol. 136, pp. 335–346, 2017, Accessed: 00, 2022. [Online]. Available: