Image icon  Austenitic stainless steel

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Description: 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.

Keywords: alloy • annealing twins • austenite • carbon • dislocation • grain • iron • metal • recrystallisation • stainless steel • steel
Categories: Science approaches > Structure, bonding & defects > Dislocations
Science approaches > Structure, bonding & defects > Twins
Science approaches > Microstructure
Materials > Metals & alloys > Stainless steels
Processes > Thermal treatments > Annealing
Testing, analysis & experimentation > Metallography
Scale > Micro
Created by: Prof H K D H Bhadeshia, Department of Materials Science and Metallurgy, University of Cambridge
DoITPoMS, University of Cambridge
Published by: DoITPoMS, University of Cambridge
License: This resource is released under the Creative Commons Attribution Non-Commercial Share Alike license (2.0 UK: England & Wales).
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Date created: 18 July 2003
Date added: 21 August 2009
Resource ID: 1803