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

DoITPoMS Micrograph Library Full Record for Micrograph 241

Full Record for Micrograph 241

Link to full size image of micrograph 241
[241 KB]

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Micrograph no
241
Brief description
Fe, C 0.3 (wt%) steel, spheroidised carbide
Keywords
alloy Link to MATTER Glossary entry for alloy, carbon, hypoeutectoid Link to MATTER Glossary entry for hypoeutectoid, iron, metal, pearlite Link to MATTER Glossary entry for pearlite, steel Link to MATTER Glossary entry for steel
Categories
Metal or alloy
System
Fe-C-X   Link to phase diagram
Composition
Fe, C 0.3 (wt%)
Standard codes
Reaction
Processing
Spheroidised
Applications
Sample preparation
Nital
Technique
Reflected light microscopy
Length bar
400 μm
Further information
A hypoeutectoid alloy (composition less than eutectoid). The first phase formed upon cooling from the austenite phase field is proeutectoid ferrite. Due to the lower solubility of carbon in ferrite, carbon is partitioned into the remaining austenite. At the eutectic point the remaining carbon-enriched austenite transforms to pearlite (a mixture of ferrite and cementite), which is the darker region of the micrograph. The proportion of pearlite is dependent upon the overall composition.

Subsequent to casting the sample was annealed for a long period just below the transformation range. This induces the cementite to take on a spherical appearance. This results in a softer and more ductile alloy. This process is known as spheroidisation. The changes to the morphology of the cementite cannot be seen clearly in this micrograph, but they are more apparent at higher magnification (see micrograph 242).
Contributor
Dr R F Cochrane
Organisation
Department of Materials, University of Leeds
Date
04/09/02
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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