Yazar "Mohagheghi, S." seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • Küçük Resim Yok
    Öğe
    On the Effect of Interphase Boundary Energy Anisotropy on Morphologies: A New Type of Eutectic Grain Observed in a Three-Phase Eutectic System
    (Springer, 2024) Mohagheghi, S.; Şerefoğlu, M.
    Eutectic microstructures are dramatically affected by the anisotropy in interphase boundary energy. Depending on this anisotropy function, different eutectic grains may grow simultaneously at the same experimental conditions. In all reported quasi-isotropic and anisotropic two-phase and three-phase eutectic grains in thin samples, lamellar morphology is observed and the microstructure is essentially two dimensional (2D), since the interphase boundaries are perpendicular to the sample walls. Using the ?(In)–In2Bi–?(Sn) system and real-time solidification experiments in thin samples, we introduce a unique and new type of anisotropic three-phase eutectic grain, entitled here as “Laminated Matrix with Rods (LMR).” In this grain, due to the anisotropy in In2Bi/?(Sn) interphase boundary, the evolving phases, and hence, the microstructures observed through the two glass plates of the thin sample are completely different, despite the strong confinement effect. During rotating directional solidification (RDS) experiments, the morphology or the aspect ratio of all phases changes periodically and drastically. Specifically, In2Bi, ?(In), and ?(Sn) phases evolve from all being lamellar perpendicular to the sample walls to the matrix, elongated/trapezoidal rods, and a lamella parallel to the sample walls, respectively. Our experimental results show that these morphological transitions are due to change in the interphase boundary orientation with respect to the growth direction. Graphical abstract: (Figure presented.) © The Author(s) 2024.
  • Küçük Resim Yok
    Öğe
    Pinning/depinning dynamics of trijunction lines during faceted/nonfaceted eutectic growth
    (Elsevier B.V., 2024) Mohagheghi, S.; Şerefoğlu, M.; Akamatsu, S.; Bottin-Rousseau, S.
    We present an in situ experimental study of decoupled- and coupled-growth patterns in a binary faceted/ nonfaceted (f/nf) eutectic alloy. Real-time optical observation is carried out at low growth velocity V (<0.3?ms?1) during directional solidification of the transparent AminoMethylPropaneDiol-Succinonitrile (AMPD-SCN) eutectic in thin samples. On a large scale, the two-phase growth front mostly exhibits irregularly spaced decoupled-growth patterns involving faceted fiber-like AMPD crystals that protrude in the liquid ahead of, and in weak diffusive interaction with the nonfaceted SCN solid. The morphological stability of low-velocity, steady-state decoupled-growth patterns is evidenced. In addition, three types of (f/nf) coupled-growth patterns with fiber-like, tubular (or “hollow”) and C-shaped morphologies, respectively, are identified. New light is cast on the pinning/depinning dynamics of trijunctions at which the two solid phases and the liquid meet in equilibrium. A discussion is initiated on the interplay between the interfacial kinetics of the more or less mobile facets and the solute diffusion field, and on the stability of triple junctions with strongly anisotropic interfaces. © 2024 Elsevier B.V.