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

DoITPoMS Micrograph Library Full Record for Micrograph 159

Full Record for Micrograph 159

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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
2 mm
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-NonCommercial-ShareAlike 4.0 International
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