Full Record for Micrograph 698

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Micrograph no
Brief description
Cu-4.5 wt% P
alloy Link to MATTER Glossary entry for alloy, bronze Link to MATTER Glossary entry for bronze, copper, coring Link to MATTER Glossary entry for coring, dendrite Link to MATTER Glossary entry for dendrite, hypoeutectic Link to MATTER Glossary entry for hypoeutectic, metal, phosphorus Link to MATTER Glossary entry for phosphorus
Metal or alloy
Cu-P   Link to phase diagram
Cu 95.5, P 4.5 (wt%)
Standard codes
This alloy has no practical applications
Sample preparation
Etch in ferric chloride
Reflected light microscopy
Length bar
50 μm
Further information
This is an example of a hypoeutectic alloy. On slow cooling the liquid first solidified at approximately 940ºC as copper rich dendrites. The composition of the remaining liquid became increasingly rich in phosphorus until it solidified as a eutectic (8.38 wt% P) at the eutectic temperature of 714ºC. Note that the dendrites are cored - the different contrast after etching indicated that the composition varies with position in the dendrites. This is caused by non-equilibrium solidification. The cooling rate was too rapid for equilibrium to be maintained between the solid and the liquid phases.

This alloy has no practical applications. Phosphor bronzes usually contain 5 wt% Sn for solid solution strengthening with 0.2 wt% P for interstitial solution strengthening. They have high strength and corrosion resistance and are usually used for springs.
Dr J Marrow
Department of Materials Science, University of Manchester and UMIST
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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