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Full Record for Micrograph 774

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Micrograph no
774
Brief description
Austenitic stainless steel
Keywords
alloy Link to MATTER Glossary entry for alloy, annealing twins Link to MATTER Glossary entry for annealing twins, austenite Link to MATTER Glossary entry for austenite, carbon, dislocation Link to MATTER Glossary entry for dislocation, grain Link to MATTER Glossary entry for grain, iron, metal, recrystallisation Link to MATTER Glossary entry for recrystallisation, stainless steel, steel Link to MATTER Glossary entry for steel
Categories
Metal or alloy
System
Fe-C-X   Link to phase diagram
Composition
Stainless steel
Standard codes
Reaction
Processing
The sample was cold-deformed by rolling and then annealed at 704°C for one hour.
Applications
Sample preparation
Technique
Transmission electron microscopy (TEM)
Length bar
1 μm
Further information
This is a transmission electron micrograph taken at 200 kV, from a thin foil sample of "302AA" austenitic stainless steel. The sample was cold-deformed by rolling and then annealed at 704°C for one hour. The image shows a beautiful picture of annealing twins. Notice how the ends of annealing twins are flat, the shape being determined by a minimisation of interfacial energy. Mechanical twins, by contrast, are lenticular (lens like) with sharply pointed ends to minimise the strain energy due to the twinning shear. Annealing twins do not cause any deformation so strain energy minimisation is not an issue. This is also the reason why there is no strain field contrast visible at the tips of the annealing twins.

Source: http://www.msm.cam.ac.uk/phase-trans/abstracts/annealing.twin.html.
Contributor
Prof H K D H Bhadeshia
Organisation
Department of Materials Science and Metallurgy, University of Cambridge
Date
18/07/03
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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