Research activity
Solidification of binary Eutectic alloys
Eutectic composites are common microstructures arising during the solidification process of various metal alloys. In relatively wide conditions, these alloys form domains of different solid phases of distinct composition. Understanding what patterns arise due to the conditions of the solidification process is important both for metallurgists, as the properties of the finished material will depend on it, and for physicists due to the interest in pattern forming systems.
The two solid phases arising during the solidification of binary eutectics, solidify either as an array of parallel lamellae, or as an array of rods of one phase surrounded by the other phase. Jackson and Hunt [Trans Metall Soc AIME, v. 236, p. 1129 (1966)] found an approximate analytical solution to the steady growth problem finding the aforementioned families of periodic patterns. The stability of these patterns has been studied extensively both in simulations and experiments for thin, quasi two-dimensional samples.
Using the phase-field method we were able to investigate the stability of lamellar patterns in massive three-dimensional samples. Results have shown that parallel lamellar patterns are obtained for a relatively large set of solidification conditions, larger than for thin samples. When solidification conditions overcome some identified limits, the pattern destabilizes forming zig-zag patters or, in more extreme conditions, producing a more drastic reshaping of the pattern which include reconnection of the lamellae and the formation of a lamellar maze.
Investigation into the stability of rods, led us to discover that rods are subjected to a bifurcation shape instability, that leads to deformations towards the first or second nearest neighbours. While the zig-zag instability for lamellae can be found in other systems, the above instability seems specific to eutectic solidification. Elongated rods however hardly connect, as if healing of defects were hindered by some kind of energetic barrier.
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Fig 1: Top-view of a solidifying eutectic binary alloy with varying concentration. As the concentration changes, solidification patterns change from rod-like to lamellar, to rod-like again. The initial configuration is an unstable lamellar pattern that quickly destabilizes into a disordered rod array. |
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Defects and Multistability in eutectic solidification patterns
A. Parisi and M. Plapp
Europhysics Letters, 90(2), 26010 (2010) [Preprint]Role of transverse temperature gradients in the generation of regular eutectic directional-solidification patterns
M. Perrut, A.Parisi, S. Akamatsu, S. Bottin-Rousseau, G. Faivre and M. Plapp
Acta Materialia, 58(5), 1761 (2010)
Stability of lamellar eutectic growth
A. Parisi and M. Plapp
Acta Materialia, 56(6), 1348 (2008)Three-dimensional phase-field simulations of eutectic solidification and comparison to in situ experimental observations
A. Parisi, M. Plapp, S. Akamatsu, S. Bottin-Rosseau, M. Perrut and G. Faivre
in "Modeling of Casting, Welding and Advanced Solidification Processes - XI", ed. by C.-A. Gandin and M. Bellet,
The Mineral Metals & Materials Society (2006) pp. 399-406 [PDFormat]Three-dimensional phase-field simulations of directional solidification
Marcus Dejmek, Roger Folch, Andrea Parisi and Mathis Plapp
in "Solidification Processes and Microstructures: a symposium in honor of Prof. W. Kurz"
The Minerals, Metals & Materials Society (2004) pp. 387-392, [Preprint]