Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Micrograph Library Full Record for Micrograph 12

Full Record for Micrograph 12

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Micrograph no
Brief description
Cu 21, Sn 79 (wt%), peritectic transformation
alloy Link to MATTER Glossary entry for alloy, bronze Link to MATTER Glossary entry for bronze, copper, metal, peritectic reaction Link to MATTER Glossary entry for peritectic reaction, tin
Metal or alloy
Cu-Sn   Link to phase diagram
Cu 21, Sn 79 (wt%)
Standard codes
As-cast (sand mould)
Sample preparation
Reflected light microscopy
Length bar
400 μm
Further information
This microstructure is generated via a peritectic reaction (L+e = eta), which bears some similarities to the more familiar eutectic reaction (L = a + b). Upon cooling from the liquid phase field, primary e is formed, which can be seen here as a slightly darker phase than the sheath of h surrounding it. The h sheath is the product of a peritectic reaction between e and liquid. The peritectic reaction rarely goes to completion, since the formation of h around the e phase separates it from the liquid and inhibits further growth. Eventually, the remaining liquid transforms by a eutectic reaction to h and Sn. In this micrograph, the constituents of the eutectic mixture cannot be distinguished and it appears uniformly dark.
Prof T W Clyne
Department of Materials Science and Metallurgy, University of Cambridge
Licence for re-use
Attribution-NonCommercial-ShareAlike 4.0 International
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