Image icon  Cu-4.5 wt% P

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Description: This is an example of a hypoeutectic alloy. On slow cooling the liquid first solidified at approximately 940°C 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 714°C. 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.
Keywords: alloy • bronze • copper • coring • dendrite • hypoeutectic • metal • phosphorus
Categories: Science approaches > Microstructure
Materials > Metals & alloys > Copper & alloys
Testing, analysis & experimentation > Metallography
Scale > Micro
Created by: DoITPoMS, University of Cambridge
Dr J Marrow, Department of Materials Science, University of Manchester and UMIST
Published by: DoITPoMS, University of Cambridge
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Date created: 07 November 2002
Date added: 21 August 2009
Resource ID: 1727