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New evidence for the dual origin of anomalous eutectic structures in undercooled Ni–Sn alloys: In situ observations and EBSD characterization

Yang, C. and Gao, Jianrong and Zhank, Yikun and Kolbe, Matthias and Herlach, Dieter M. (2011) New evidence for the dual origin of anomalous eutectic structures in undercooled Ni–Sn alloys: In situ observations and EBSD characterization. Acta Materialia, 59, pp. 3915-3926. DOI: 10.1016/j.actamat.2011.03.016.

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Abstract

Rapid solidification processes of glass-fluxed Ni81.3Sn18.7 eutectic alloys at various undercoolings were observed in situ using a highspeed camera. The microstructure of the samples was characterized using optical microscopy, scanning electron microscopy and electron back-scattering diffraction analysis. It was found that the recalescence front sweeps the sample surface from one side to the other, which coincides with the formation of a directional solidification microstructure. Such a finding suggests that it is feasible to measure crystal growth velocities in the undercooled liquid by tracking the loci of the recalescence front. The measured data show sudden acceleration of crystal growth kinetics at a medium undercooling, giving evidence for a transition from coupled growth to uncoupled growth. Microscopic studies revealed that the sample with an undercooling of 202 K comprises two types of anomalous eutectic, which are distinguished by the size and orientations of Ni-rich grains. The results verify a recent hypothesis that anomalous eutectic in undercooled Ni–Sn alloys has a dual origin: it results from eutectic dendrites growing at low undercoolings and from single-phase Ni-rich dendrites growing at high undercoolings.

Document Type:Article
Title:New evidence for the dual origin of anomalous eutectic structures in undercooled Ni–Sn alloys: In situ observations and EBSD characterization
Authors:
AuthorsInstitution or Email of Authors
Yang, C.Northeastern University Shenyang
Gao, JianrongNortheastern University Shenyang
Zhank, YikunNortheastern University Shenyang
Kolbe, Matthiasmatthias.kolbe@dlr.de
Herlach, Dieter M.dieter.herlach@dlr.de
Date:26 April 2011
Journal or Publication Title:Acta Materialia
Refereed publication:Yes
In Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:59
DOI:10.1016/j.actamat.2011.03.016
Page Range:pp. 3915-3926
Status:Published
Keywords:Undercooling, non-equilibrium solidification, eutectic growth, eutectic microstructures
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W FR - Forschung unter Weltraumbedingungen (old)
DLR - Research area:Space
DLR - Program:W FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):W - Vorhaben Materialwissenschaftliche Forschung (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Physics in Space
Deposited By: Dieter Herlach
Deposited On:02 May 2011 09:50
Last Modified:26 Mar 2013 13:28

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