On the Growth Dynamics of Nearly-Locked Grain in the Three-Phase In-Bi-Sn Eutectic System

We present an in-situ experimental investigation of irregular eutectic growth dynamics observed optically in real time during directional solidification (DS) and rotating directional solidification (RDS) of a model transparent alloy, namely Amino-methyl-propanediol-Succinonitrile (AMPD-SCN). The SCN-rich solid grows with a nonfaceted solid-liquid interface, while AMPD forms thin whisker-like faceted crystals. With RDS, we observed simultaneously four distinct growth dynamics along the solidification front thanks to the rotation induced velocity ramp. At low velocity, AMPD crystals grow individually, with their leading tip ahead of – at a higher temperature than – the SCN-liquid interface which presents a linear undercooling change with V ramp. This regime is defined as a quasi-steady decoupled growth. During RDS, AMPD crystals are found to rotate with the sample in this regime. When they can reach the unsteady coupled-growth regime at higher V, since increasing V favors the formation of AMPD-SCN-liquid trijunctions, they start to branch noncrystallographically. At higher velocity, impurity effects lead to the formation of two-phase fingers. Further increase in the velocity results in the formation of primary SCN dendrites and a fine interdendritic eutectic microstructure. DS experiments confirmed the existence of those regimes at different velocities.

supporting

confidence: 65%

mentioning

confidence: 99%

In-situ investigation of the solidification dynamics in an irregular eutectic alloy

Mohagheghi

Bottin-Rousseau²,

Şerefoğlu³

2023

“…A comparison between a comprehensive Laue microdiffraction analysis and EBSD measurements in a reference sample will be presented in a separate publication. Finally, further experimental information on the anisotropy of the interphase boundaries should be obtained via the socalled rotational directional solidification method [20,21].…”

Section: Discussionmentioning

confidence: 99%

Formation of locked-lamellar grains in a slightly hypoeutectic Al-Al₂Cu alloy during thin-sample directional solidification

Medjkoune

Bottin-Rousseau

Carroz

et al. 2023

We studied the formation and growth of locked-lamellar microstructures in a thin sample of a slightly hypoeutectic Al-Al2Cu alloy. The coupled-growth dynamics, including early stages and steady-state regimes, was observed optically in real time during directional solidification. The orientation of the α (Al) and θ (Al2Cu) crystals was measured ex situ in a series of eutectic grains by X-ray Laue microdiffraction. A nucleation event of a θ crystal on a pre-existing α crystal, and the subsequent growth of a eutectic grain with a type-C orientation relationship, that is, with a coincidence of {123}-α and {100}-θ planes, were observed in situ. In type-C eutectic grains, lamellar locking occurred parallel to the low-energy coincidence plane. A regular (floating) coupled-growth dynamics was observed in misoriented eutectic grains.

“…Indeed, within the symmetric-pattern approximation, the RDS microstructure is homothetic to the shape of the interphase boundaries predicted by the Wulff construction [53]. A more recent RDS setup has been built by Melis Şerefoğlu in her laboratory in Turkey, and used, in particular, for the study of interfacial-anisotropy effects in ternary, three-phased eutectics [54]. The next step was to establish a clear link between the locked-lamellar growth dynamics, the presence of deep minima in the -plot, and coincidence planes in anisotropic eutectic grains.…”

Section: Anisotropy Effectsmentioning

confidence: 99%

Gabriel Faivre: his legacy on eutectic solidification

Akamatsu

2023

In the honor of Gabriel Faivre (1944-2020), I will present a review of major scientific contributions to the understanding of the dynamics of eutectic growth patterns. From the end of the 1980s, Gabriel Faivre undertook a systematic research in solidification guided by the new concepts of the nonlinear physics of out-of-equilibrium pattern formation. Drawing on his outstanding capabilities as an experimentalist, he refined the method of in situ directional solidification of model alloys. With constant reference to physics and metallurgy, he succeeded in carrying out a high-level research, keen to reach strong qualitative impact and quantitative accuracy. Gabriel Faivre made key discoveries, together with coworkers and young researchers in Paris, and in collaboration with materials scientists and physicists in France and abroad. From symmetry breaking instabilities to eutectic cells and dendrites, over rod-like and labyrinth patterns, full light has been shed onto new phenomena, fascinating to the eye and the mind. During the last decade, Gabriel Faivre mentored an in-depth analysis of interfacial-anisotropy effects on coupled-growth patterns, thus reconciliating the theories of regular eutectics and crystal-orientation dependent eutectic-grain growth. Being both a rigorous scientist and a generous colleague, he left us a vast legacy of prospective research topics in solidification and crystal-growth science. Sharing his knowledge of fine arts and humanities, Gabriel Faivre also instilled the best of intellectual thinking in those who were fortunate enough to work with him.