Cao, L, Cochrane, RF and Mullis, AM (2015) Solidification morphology and phase selection in drop-tube processed Ni-Fe-Si intermetallics. Intermetallics, 60. 33 - 44. ISSN 0966-9795
Abstract
Drop-tube processing was used to rapidly solidify droplets of Ni64.7Fe10Si25.3 and Ni59.7Fe15Si25.3 alloys. In the larger droplets, and therefore at low cooling rates, only two phases, γ-Ni31Si12 and β1-Ni3Si were observed. Conversely, in the smaller droplets, and therefore at higher cooling rates, the metastable phase Ni25Si9 was also observed. The critical cooling rate for the formation of Ni25Si9 was estimated as 5×103 K s-1. SEM and TEM analysis reveals three typical microstructures: (I) a regular structure, comprising single-phase γ-Ni31Si12 and a eutectic structure between γ-Ni31Si12 and β1-Ni3Si; (II) a refined lamellar structure with a lamellar spacing < 50 nm comprising γ-Ni31Si12 and β1-Ni3Si; (III) an anomalous structure with a matrix of Ni25Si9 and only a very small proportion of a second, and as yet unidentified, phase. These results indicate that there is an extended stability field for Ni25Si9 in the Ni-rich part of the Ni-Fe-Si ternary system in comparison to the Ni-Si binary system. With an increase of cooling rate, an increasing fraction of small droplets experience high undercoolings and, therefore, can be undercooled into the Ni25Si9 stability field forming droplets consisting of only the anomalous structure (III). The Fe atoms are found to occupy different substitutional sites in different phase, i.e. Fe substitutes for Ni in the γ phase and Si in the L12 (β1) phase respectively.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015 Elsevier Ltd. All rights reserved. NOTICE: this is the author’s version of a work that was accepted for publication in Intermetallics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Intermetallics, 60, (2015) DOI 10.1016/j.intermet.2015.01.006 |
Keywords: | Intermetallics; Rapid solidification; Microstructure |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemical & Process Engineering (Leeds) > Institute for Materials Research (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 18 Mar 2015 16:41 |
Last Modified: | 28 Jan 2018 15:23 |
Published Version: | http://dx.doi.org/10.1016/j.intermet.2015.01.006 |
Status: | Published |
Publisher: | Elsevier |
Identification Number: | 10.1016/j.intermet.2015.01.006 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:83569 |