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

DoITPoMS Micrograph Library Micrograph 1 and full record

Micrograph 1 and full record

Link to image file for micrograph 1
Micrograph no
Brief description
Al 75, Cu 25 (wt%), hypoeutectic alloy
alloy Link to MATTER Glossary entry for alloy, aluminium Link to MATTER Glossary entry for aluminium, copper, dendrite Link to MATTER Glossary entry for dendrite, hypoeutectic Link to MATTER Glossary entry for hypoeutectic, lamella Link to MATTER Glossary entry for lamella, metal
Metal or alloy
Al-Cu   Link to phase diagram
Al 75, Cu 25 (wt%)
Standard codes
Sand cast
Sample preparation
Etched in sodium hydroxide solution
Reflected light microscopy
Length bar
40 μm
Further information
The micrograph shows primary Al dendrite arms (white). The dendrite trunk has been intersected at an angle by the plane of polishing to give the observed morphology. Between the dendrites is the Al - CuAl2 eutectic. Initially dendrites would have formed from the liquid, the regions between the dendrite arms known as the mushy zone transforming to a eutectic solid (L to Al + CuAl2). These two phases form cooperatively as neighbouring lamellae with the lateral diffusion of material across the growing interface. The relative amounts of the two phases (Al and CuAl2 ) within the eutectic are determined by applying the Lever Rule at the eutectic temperature.
Prof T W Clyne
Department of Materials Science and Metallurgy, University of Cambridge
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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