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Title: Heterogeneous Nucleation and Grain Initiation on a Single Substrate
Authors: Fan, Z
Men, H
Keywords: heterogeneous nucleation;grain initiation;MD simulation;interface;growth
Issue Date: 30-Aug-2022
Publisher: MDPI AG
Citation: Fan, Z. and Men, H. (2022) 'Heterogeneous Nucleation and Grain Initiation on a Single Substrate', Metals, 12 (9), pp. 1454, pp. 1 - 19. doi: 10.3390/met12091454.
Abstract: Copyright: © 2022 by the authors. Recently, we have proposed a new framework for early stages solidification, in which heterogeneous nucleation and grain initiation have been treated as separate processes. In this paper, we extend our atomic-level understanding of heterogeneous nucleation to spherical cap formation for grain initiation on a single substrate using molecular dynamics calculations. We first show that heterogeneous nucleation can be generally described as a three-layer mechanism to generate a two-dimensional (2D) nucleus under a variety of atomic arrangements at the solid/substrate interface. We then introduce the atomistic concept of spherical cap formation at different grain initiation undercoolings (ΔTgi) relative to nucleation undercooling (ΔTn). When ΔTn < ΔTgi, the spherical cap formation is constrained by the curvature of the liquid/solid interface, produces a dormant cap, and further growth is only made possible by increasing undercooling to overcome an energy barrier. However, when ΔTn > ΔTgi, spherical cap formation becomes barrierless and undergoes three distinctive stages: heterogeneous nucleation to produce a 2D nucleus with radius, rn; unconstrained growth to deliver a hemisphere of rN (substrate radius); and spherical growth beyond rN. This is followed by a theoretical analysis of the three-layer nucleation mechanism to bridge between three-layer nucleation, grain initiation and classical nucleation theory.
Description: Data Availability Statement: All data are available in the main text.
Other Identifiers: 1454
Appears in Collections:Brunel Centre for Advanced Solidification Technology (BCAST)

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