Metals 2014, 4(2), 196-234; doi:10.3390/met4020196
Review

Non-Equilibrium Solidification of Undercooled Metallic Melts

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Received: 15 May 2014; in revised form: 3 June 2014 / Accepted: 4 June 2014 / Published: 20 June 2014
(This article belongs to the Special Issue Advances in Solidification Processing)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: If a liquid is undercooled below its equilibrium melting temperature an excess Gibbs free energy is created. This gives access to solidification of metastable solids under non-equilibrium conditions. In the present work, techniques of containerless processing are applied. Electromagnetic and electrostatic levitation enable to freely suspend a liquid drop of a few millimeters in diameter. Heterogeneous nucleation on container walls is completely avoided leading to large undercoolings. The freely suspended drop is accessible for direct observation of rapid solidification under conditions far away from equilibrium by applying proper diagnostic means. Nucleation of metastable crystalline phases is monitored by X-ray diffraction using synchrotron radiation during non-equilibrium solidification. While nucleation preselects the crystallographic phase, subsequent crystal growth controls the microstructure evolution. Metastable microstructures are obtained from deeply undercooled melts as supersaturated solid solutions, disordered superlattice structures of intermetallics. Nucleation and crystal growth take place by heat and mass transport. Comparative experiments in reduced gravity allow for investigations on how forced convection can be used to alter the transport processes and design materials by using undercooling and convection as process parameters.
Keywords: undercooling; containerless solidification; metastable solids; dendrite growth; supersaturated alloys; disordered superlattices; grain refinement; forced convection; microgravity
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MDPI and ACS Style

Herlach, D.M. Non-Equilibrium Solidification of Undercooled Metallic Melts. Metals 2014, 4, 196-234.

AMA Style

Herlach DM. Non-Equilibrium Solidification of Undercooled Metallic Melts. Metals. 2014; 4(2):196-234.

Chicago/Turabian Style

Herlach, Dieter M. 2014. "Non-Equilibrium Solidification of Undercooled Metallic Melts." Metals 4, no. 2: 196-234.

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