Roll-bonded aluminium alloy diffusion couple annealed for 30 minutes at 600°C.

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Description:	This micrograph shows the grain structure of a roll-bonded aluminium alloy diffusion couple annealed for 30 minutes at 600°C. The upper half of the couple is Al-0.5Fe-1.0Mn (wt.%), the lower half is Al-1.0Si (wt.%). Annealing has recrystallised the microstructure. The Al-Fe-Mn alloy has many intermetallic particles (the dark phase). These help create recrystallisation nuclei, hence this alloy has a high density of small grains relative to the Al-Si alloy. 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. Strain of the aluminium matrix during rolling around the intermetallic particles in the Al-Fe-Mn alloy produces a high density of dislocations. Because recovery of the dislocations creates nuclei for recrystallisation, this high defect density results in a much finer recrystallised grain structure than in the particle-free Al-Si alloy.
Keywords:	alloy • aluminium • diffusion couple • metal • recrystallisation • roll-bonding
Categories:	Science approaches > Structure, bonding & defects > Dislocations Science approaches > Microstructure Science approaches > Diffusion Science approaches > Strengthening mechanisms > Recovery, recrystallisation & grain growth Materials > Metals & alloys > Aluminium & alloys Processes > Thermal treatments > Annealing Testing, analysis & experimentation > Metallography Scale > Micro
Created by:	D T L Alexander, 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). You are free: to share – to copy, distribute and transmit the work to remix – to adapt the work Under the following conditions: attribution – You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work). noncommercial – You may not use this work for commercial purposes. share alike – If you alter, transform, or build upon this work, you may distribute the resulting work only under the same or similar license to this one. View the full legal code here.
Date created:	21 May 2002
Date added:	21 August 2009
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Resource ID:	1194
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