Three-Phase Eutectic Microstructures: Influence of Interfacial Energy Anisotropy and Solute Diffusivities

Khanna, S and Choudhury, A (2021) Three-Phase Eutectic Microstructures: Influence of Interfacial Energy Anisotropy and Solute Diffusivities. In: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 52 . pp. 4246-4263.

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Abstract

In this paper, we study three dimensional microstructural evolution in a symmetric ternary three-phase eutectic alloy using phase-field simulations under directional solidification conditions. While previous studies have explored the influence of volume fractions, difference in solid-liquid interfacial energies, velocity changes, etc. on the microstructural evolution, in this paper we deal with two unexplored fundamental aspects, namely the influence of solid-solid interfacial energy anisotropy as well as the disparity in the solute diffusivities in the liquid phase on three-phase microstructure formation. We begin by comparing the undercooling vs spacing variations for different steady state microstructures like the three-fibrous (hexagonal), brick-type and lamellar morphology under symmetric conditions and estimate the stability limits for each of the patterns for spacing variations. Thereafter, we investigate the transformation of the three-fibrous (hexagonal) arrangement to lower symmetry patterns upon imposition of anisotropy in the solid-solid interfacial energy as well as a solutal diffusivity contrast in the liquid. These simulations in constrained settings provide insights about the possible mechanisms of morphological transition and reveal steady state patterns that emerge under the individual and combined asymmetries arising due to anisotropy in solid-solid interfacial energy as well as disparate solute diffusivities. Subsequently, we perform extended simulations from random initial conditions for investigating morphology selection, and quantitative parameters like the interface length between the solid phases, number and spatial distribution of fibers are utilized to characterize and understand the morphologies. The simulation study reveals that diverse microstructures similar to reported experimental observations are obtained by varying just the interfacial energy anisotropy and the diffusivity matrix, even when each of the eutectic solid phases is at an equal one-third volume fraction. Thus, assessing the strength and form of anisotropy in the solid-solid interfaces as well as the diffusivity matrices are critical to the investigation of microstructural evolution during eutectic growth in multicomponent alloys. © 2021, The Minerals, Metals & Materials Society and ASM International.

Item Type:	Journal Article
Publication:	Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Publisher:	Springer
Additional Information:	The copyright for this article belongs to Springer
Keywords:	Anisotropy; Diffusion; Eutectics; Interfacial energy; Liquids; Microstructural evolution; Morphology; Setting; Volume fraction, Interfacial energy anisotropies; Morphological transitions; Phase-field simulation; Quantitative parameters; Random initial conditions; Solid-liquid interfacial energy; Solid-solid interfaces; Three phase microstructure, Phase interfaces
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	16 Nov 2021 10:35
Last Modified:	16 Nov 2021 10:35
URI:	http://eprints.iisc.ac.in/id/eprint/69691

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