Cao, L, Cochrane, RF and Mullis, AM (2015) Microstructural Evolution and Phase Formation in Rapidly Solidified Ni-25.3 At. Pct Si Alloy. Metallurgical and Materials Transactions A, 46 (10). 4705 - 4715. ISSN 1073-5623
Abstract
The drop-tube technique was used to solidify droplets of the Ni-25.3 at. pct Si alloy at high cooling rates. XRD, SEM, and TEM analysis revealed that the metastable phase, Ni25Si9, formed as the dominant phase in all ranges of the droplets, with γ-Ni31Si12 and β 1-Ni3Si also being present. Three different microstructures were observed: the regular and anomalous eutectic structures and near single-phase structure containing small inclusions of a second phase, termed here as heteroclite structure. Both eutectic structures comprise alternating lamellae of Ni25Si9 and β 1-Ni3Si, which, we conjecture, is a consequence of an unobserved eutectic reaction between the Ni25Si9 and β 1-Ni3Si phases. The matrix of the heteroclite structure is also identified as the metastable phase Ni25Si9, in which twined growth is observed in the TEM. As the cooling rate is increased (particle size decreased), the proportion of droplets displaying the entire heteroclite structure tends to increase, with its fraction increasing from 13.91 pct (300 to 500 µm) to 40.10 pct (75 to 106 µm). The thermodynamic properties of the Ni25Si9 phase were also studied by in-situ heating during XRD analysis and by DTA. This showed the decomposition of Ni25Si9 to β 1 and γ-Ni31Si12 for temperatures in excess of 790 K (517 °C).
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2015, The Minerals, Metals & Materials Society and ASM International. This is an author produced version of a paper published in Metallurgical and Materials Transactions A. The final publication is available at Springer via http://dx.doi.org/10.1007/s11661-015-3070-6.Uploaded in accordance with the publisher's self-archiving policy. |
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: | 06 Aug 2015 13:59 |
Last Modified: | 26 Oct 2016 09:16 |
Published Version: | http://dx.doi.org/10.1007/s11661-015-3070-6 |
Status: | Published |
Publisher: | Springer Verlag |
Identification Number: | 10.1007/s11661-015-3070-6 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:88806 |