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

DoITPoMS Micrograph Library Micrograph 158 and full record

Micrograph 158 and full record

Link to image file for micrograph 158
Micrograph no
Brief description
Roll-bonded aluminium alloy diffusion couple in the as-rolled condition.
alloy Link to MATTER Glossary entry for alloy, aluminium Link to MATTER Glossary entry for aluminium, diffusion couple Link to MATTER Glossary entry for diffusion couple, metal, roll-bonding Link to MATTER Glossary entry for roll-bonding
Metal or alloy
Al, Fe 0.5, Mn 1.0 / Al, Si 1.0 (wt%)
Standard codes
Mechanical roll-bonding; reduction in thickness of about 90%.
The couple was made to investigate diffusion of silicon through the Al-0.5Fe-1.0Mn (wt.%) alloy during annealing.
Sample preparation
Electrolytically etched using Barker's reagent.
Cross-polarised light microscopy
Length bar
400 μm
Further information
This micrograph shows the grain structure of a roll-bonded aluminium alloy diffusion couple in the as-rolled condition. The upper half of the couple is Al-0.5Fe-1.0Mn (wt.%), the lower half is Al-1.0Si (wt.%). Rolling heavily deforms the microstructure, producing thin, elongated grains parallel to the roll-bonded interface.

The Barker's etch produces a thick oxide layer on the grains of aluminium (anodising). When viewed in cross-polarised light, interference in the oxide layer produces colours which depend on grain orientation, hence the grain structure is imaged. Prior to roll-bonding the Al-Si alloy was solution-treated, creating recrystallized grains that were much larger than the cellular microstructure of the Al-Fe-Mn alloy. This difference in scale of microstructure can be seen in the rolled diffusion couple.
D T L Alexander
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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