Micrograph 233 and full record
- Micrograph no
- 233
- Brief description
- Hypoeutectoid steel, normalised at 1100°C
- Keywords
- alloy , carbon, hypoeutectoid , iron, metal, pearlite , steel
- Categories
- Metal or alloy
- System
- Fe-C-X
- Composition
- Fe, C 0.4 (wt%)
- Standard codes
- Reaction
- Processing
- Normalised 1100°C
- Applications
- Sample preparation
- Nital
- Technique
- Reflected light microscopy
- Length bar
- 400 μm
- Further information
- A hypoeutectoid alloy (carbon 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 eutectoid 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.
The ferrite (light areas) is a good example of an allotriomorphic ferrite. This means that its shape does not reflect its internal crystalline symmetry as it nucleates on the austenite grain boundaries and hence follows the shape of the boundaries, the remaining austenite within the ferrite then transforms to pearlite, and is surrounded by the ferrite. The large size of the areas of pearlite arises due to the high normalisation temperature which causes the austenite grains to grow large. - Contributor
- Dr R F Cochrane
- Organisation
- Department of Materials, University of Leeds
- Date
- 04/09/02
- Licence for re-use
- Attribution-NonCommercial-ShareAlike 4.0 International
- Related micrographs
- Micrograph 234: Hypoeutectoid steel, normalised at 1100°C (200 μm)
- Micrograph 235: Hypoeutectoid steel, normalised at 950°C (400 μm)
- Micrograph 236: Hypoeutectoid steel, normalised at 950°C (100 μm)
- Micrograph 237: Hypoeutectoid steel, normalised at 950°C (400 μm)
- Micrograph 238: Hypoeutectoid steel, normalised at 950°C (100 μm)
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