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Full Record for Micrograph 614

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Micrograph no
614
Brief description
Rapid solidification in an atomised droplet
Keywords
alloy Link to MATTER Glossary entry for alloy, atomising Link to MATTER Glossary entry for atomising, droplet, hypercooled, latent heat Link to MATTER Glossary entry for latent heat, metal, rapid solidification, recalescence, soldidification
Categories
Metal or alloy
System
Al-Mg   Link to phase diagram
Composition
Al 90, Mg 10 (wt%)
Standard codes
Reaction
N/A
Processing
Rapid solidification of an atomised droplet
Applications
Rapid solidification processing reduces the scale of microsegregation and increases solid solubility (allowing subsequent fine-scale precipitation). 'Glassy' (vitrified) metals can be produced.
Sample preparation
Technique
Transmission electron microscopy (TEM)
Length bar
500 nm
Further information
Because of the fine scale of the droplet, heat extraction is very rapid, and large undercoolings are achieved before crystal nucleation can begin. Thus, in this droplet, the solidification front has advanced very rapidly through the droplet from the nucleation point (on the surface at the left of the image). Its velocity is initially so great that no interfacial breakdown is possible. As the front advances, however, latent heat is evolved and this 'recalescence' reduces the rate of solidification to a point where interfacial breakdown is possible and a cellular structure is observed in the last region to solidify (at the right hand side of the image).
Contributor
Prof T W Clyne
Organisation
Department of Materials Science and Metallurgy, University of Cambridge
Date
03/10/02
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales