Frontiers in Solidification Science VIII: Eutectic Growth
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Chemistry and Physics of Materials Committee, TMS: Phase Transformations Committee, TMS: Solidification Committee, TMS: Computational Materials Science and Engineering Committee
Program Organizers: Damien Tourret, IMDEA Materials Institute; Amy Clarke, Los Alamos National Laboratory; Ulrike Hecht, Access e.V.; Nana Ofori-Opoku, Canadian Nuclear Laboratories; Melis Serefoglu, Marmara University; Tiberiu Stan, Asml
Tuesday 8:30 AM
March 16, 2021
Room: RM 56
Location: TMS2021 Virtual
Session Chair: Nathalie Mangelinck-Noël, Aix Marseille Univ. CNRS, IM2NP UMR 7334; Melis Şerefoğlu, Koç University; Sabine Bottin-Rousseau, Sorbonne University; Ulrike Hecht, Access e.V.
8:30 AM Invited
Coupled and Decoupled Eutectic Growth in a Transparent Irregular Eutectic Alloy: Sabine Bottin-Rousseau1; Samira Mohagheghi2; Silvère Akamatsu1; Melis Serefoglu2; 1Sorbonne University; 2Koç University
We present an experimental study of irregular eutectic growth patterns during directional solidification of the transparent faceted/nonfaceted AMPD-SCN alloy in thin samples. Real-time observations were performed with a regular optical microscope. The pulling velocity V was varied between 0.01 and 2 µm/s. We identified three different two-phase growth regimes as a function of V: (i) quasi-steady decoupled growth at low V values, during which the leading tips of well-separated, needle-shaped AMPD crystals were growing ahead of the SCN matrix; (ii) unsteady coupled growth at intermediate V values, with frequent noncrystallographic branching of the AMPD crystals; (iii) two-phase fingers at higher velocities (destabilizing effect of residual impurities). The labile pinning of the solid(AMPD)-solid(SCN)-liquid trijunctions involving faceted interfaces was key to the observed morphological transitions. In particular, we discovered that noncrystallographic branching operated near the trijunctions.Work financed by Campus France (PHC BOSPHORUS 39706RE) and TÜBİTAK (Grant no 217M089).
9:00 AM
Crystal-orientation Maps of Lamellar Eutectic Growth Microstructures in Thin Al-Al2Cu Films Obtained by Laue Microdiffraction: Mehdi Medjkoune1; Silvère Akamatsu1; Geoffroy Prévot1; Jean-Sébastien Micha2; Sabine Bottin-Rousseau1; 1Nanoscience institute of Paris; 2European Synchrotron ESRF, CRG IF Beamline BM32
We present the first Laue microdiffraction study of crystal orientation relationships (ORs) in lamellar microstructures obtained by directional solidification in thin Al-Al2Cu samples. We focus on the “lamellar-locking” phenomenon, which is linked to the presence of deep minima of the free energy of the interphase boundary when it aligns with a coincidence plane. In order to establish a precise link between that anisotropy, the OR, and the inclination of the lamellae, local crystallographic analysis is essential. We performed Laue microdiffraction at the ESRF synchrotron (BM32 facility). This provides a non-destructive and spatially resolved technique using a 0.5µm polychromatic x-ray micro-beam. The measurements deliver two-dimensional scans of selected areas (typically 100X100 µm2) of the metallic film. We will give useful details on the analysis of Laue microdiffraction patterns. We discovered that the emerging ORs depend on the alloy concentration. We initiate a discussion on the mosaicity of the composite films.
9:20 AM
Coexistence of Rod-like and Lamellar Eutectic Growth Patterns: In Situ Experiments in Microgravity: Silvere Akamatsu1; Sabine Bottin-Rousseau2; Mathis Plapp3; Victor Witusiewicz4; Ulrike Hecht4; 1Cnrs; 2Sorbonne University; 3Ecole Polytechnique; 4Access eV
We present real-time observations of a lamellar-to-rod transition during directional solidification of a model transparent eutectic alloy. In order to avoid thermosolutal convection in the liquid, in situ experiments –the first of their kind– were carried out under microgravity onboard the ISS (ESA/NASA project TRANSPARENT ALLOYS). Previous studies (on ground) brought important results on the dynamics of lamellar and rod-like eutectic patterns in separate systems. Here, we discovered a way, based on the use of a transverse temperature gradient, to maintain a coexistence between extended rod-like and lamellar domains over large time and space scales. The lamella/rod instability mode, the dynamics of the boundary between the two domains, and possible crystallographic effects will be discussed. We will compare our observations with previous ex situ observations in metallic ingots, and recent numerical simulations. This growth dynamics leads to the freezing of an interesting composite architecture in the bulk solid.
9:40 AM
Phase-field Simulations of the Lamella-to-rod Transition in Eutectic Solidification: Mathis Plapp1; Sabine Bottin-Rousseau2; Silvère Akamatsu2; 1Ecole Polytechnique, CNRS; 2Sorbonne Université, CNRS
It is well known that the two most frequently observed microstructures for directionally solidified eutectic composites are lamellae and rods. Recently, it was observed in microgravity experiments that a rod state can be progressively replaced by lamellae that grow normal to a sample wall. We investigate the conditions for the occurrence of this phenomenon with the help of three-dimensional phase-field simulations and find that (i) a transverse temperature gradient is necessary, (ii) the lamellae can grow only if the volume fraction of the minority phase is above a critical value, (iii) this critical value depends on the solidification rate, and (iv) the resulting fronts are typically strongly heterogeneous, with lamellae and rods coexisting in many different geometries. It was observed in previous simulations that the instability leading from lamellae to rods is propagativein nature. This instability is quantitatively studied.
10:00 AM
Orientation Relationships and Pattern Evolution In Directionally Solidified Al-Cu-Mg Ternary Eutectic
: Dominic Ezemenaka1; Amber Schneeweis Genau1; 1University of Alabama at Birmingham
Microstructure formation in multi-phase, multi-component systems is often highly sensitive to both processing parameters and small changes in composition. In this work, directional solidification via a Bridgman-type furnace is used to explore the behavior of alloys at or near the Al-Al2Cu-Al2CuMg ternary eutectic point. The stability limits of couple growth are considered, and a semi-automated method of image analysis used to quantify changes to the solidification microstructure as a function of both thermal gradient and growth rate. Since there exist incomplete literature data on this system’s preferred crystal orientation relationships and how those orientations develop with increasing growth height, this research also seeks to deploy both electron backscatter diffraction (EBSD) and scanning electron microscopy (SEM) techniques to expand our understanding on the subject matter. The results will be compared with the behavior of Al-Cu-Ag ternary eutectic, which shares two of the same phases.
10:20 AM Invited
Phase Field Modeling of Solidification with Application to Template-directed Solidification: Erik Hanson1; David Montiel1; Katsuyo Thornton1; 1University of Michigan
This talk will focus on the application of phase field modeling to study template-directed eutectic solidification, in which a melt at the eutectic composition is solidified in a confined environment of the template with regular structure. Microstructures with patterns emerges during the solidification process due to the interactions between the solidification front and the template surfaces, along with the lamellar pattern that arises naturally from eutectic solidification. We will describe the insights provided by phase field simulations on how the template induces reorientation of the lamellae, how the morphologies change from lamellae to ring-like patterns, and finally how Archimedean lattices arises, as well as how all these structures can be tuned by the processing conditions (e.g., solidification velocity) and the template geometry. We will also highlight the application of PRISMS-PF to solidification, an open-source framework for phase-field simulations of microstructure evolution, developed with an emphasis on performance, flexibility, and ease-of-use.
10:50 AM
Probing the Growth Dynamics of Eutectic Colonies in Zn-Al via X-ray Video Microscopy: Yeqing Wang1; Jianrong Gao2; Ashwin Shahani1; 1University of Michigan; 2Northeastern University
Eutectic Zn-Al is an attractive anode material for aqueous rechargeable batteries. It is of fundamental and technical interest to investigate their solidification behavior in casting. In this work, we probe the eutectic solidification process in Zn-5wt%Al alloys via synchrotron-based, in situ X-ray radiography. We observe the formation and elimination of two‑phase cells or colonies as growth proceeds, suggesting that the solidification front is inherently unstable. Colonies increase in number when one colony splits into two, and decrease in number when one colony is overgrown by its neighbors, in agreement with recent phase field simulations. Our results also demonstrated that the relationship between undercooling and growth velocity does not agree with predictions from the Jackson-Hunt criterion, owing to the presence of thermo-solutal convection. The evolution of the eutectic colonies, and their interaction with fluid flow, will be presented and discussed.
11:10 AM
Lamellar Spacing Selection during Oscillatory Eutectic Solidification: Paul Chao1; Ashwin Shahani1; 1University of Michigan
A number of fundamental questions remain unanswered regarding the dynamics of eutectic patterns with isotropic interfaces. Here, we observe experimentally the solidification behavior of an Al-Cu binary eutectic as a model system using a novel imaging approach that combines in-situ X-ray radiography and ex-situ X-ray tomography. The former allows us to trace the solid-liquid interfaces while the latter enables us to visualize the solid-solid interfaces. When put together, we can quantify the development of a highly branched and three-dimensional microstructure in the presence of an oscillatory solid-liquid interface velocity. These details provide direct insight into the mechanism of lamella creation and elimination as the lamellar spacing accommodates fluctuations in growth velocity. Our quasi-4D tomography approach holds broad appeal to the solidification science community, as it can temporally resolve the solidification process on the order of seconds and spatially resolves individual lamellae on the order of micrometers.
11:30 AM
Phase Field Modeling of Biomineralization?
Microstructure Evolution in Mollusk Shells
: Laszlo Granasy1; Laszlo Ratkai1; Tamas Pusztai1; 1Wigner Research Centre for Physics
During biomineralization, complex hierarchically structured organo-mineral composites form. In a few cases, crystallization is controlled by the biological system via adjusting the composition of the mother phase. We explore the possibility that phase-field approaches developed for describing complex polycrystalline structures can be adapted to such biological crystallization processes. Microstructure evolution during the formation of shells of three mollusks (a bivalve: Unio pictorum, a cephalopod: Nautilus pompilius, and a gastropod: Haliotis asinina) are investigated. In these cases, electron microscopy reveals a common sequence of ultrastructures: globular, columnar (prismatic), and the layered nacreous domains, when moving inwards from the outer surface of the shell. We present a minimum model that captures several aspects of microstructure evolution in these cases. An orientation field based phase-field technique developed to model multigrain eutectic solidification is used. With appropriate choice of the model parameters microstructures resembling closely to the experimental ones can be obtained.