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

DoITPoMS Micrograph Library Full Record for Micrograph 611
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Full Record for Micrograph 611

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Micrograph no
611
Brief description
Section of a metal matrix composite (MMC) after extrusion and annealing
Keywords
alumina Link to MATTER Glossary entry for alumina, annealing Link to MATTER Glossary entry for annealing, coincidence site lattice (CSL), composite material Link to MATTER Glossary entry for composite material, extrusion Link to MATTER Glossary entry for extrusion, island grains, MMC, nucleation Link to MATTER Glossary entry for nucleation, particle, stringers
Categories
Composite
System
Al
Composition
Commercial purity (99.5%) + 13 micron alumina spheroids
Standard codes
Reaction
N/A
Processing
Commercial purity (99.5%) aluminium has been atomised, thoroughly mixed with alumina reinforcement particles and then extruded.
Applications
Metal matrix composites (MMCs) offer high specific stiffness which can be retained to high temperatures. This makes them suitable for applications in the aerospace industry. They also offer controlled (or zero) thermal expansion coefficients, good wear resistance and good impact properties.
Sample preparation
The sample has been oxidised to provide colour contrast for different grain orientations.
Technique
Reflected light microscopy, polarised
Length bar
40 μm
Further information
Commercial purity aluminium has atomised, mixed with 13 micron spherical alumina particles, ball milled, tumbled, cold compacted (20MPa) and then extruded (with the working direction vertical in the image). It has then been annealed at 630 degrees C. Vertical stringers of fine oxide particles are visible. Note the small yellow 'island' grain which has formed within one of the recrystallised grains and is likely to have nucleated on the adjacent reinforcement particle. Note also the boundary facets of some grains. These indicate a preferred habit plane and are probably coincidence site lattice (CSL) boundaries.
Contributor
Prof T W Clyne
Organisation
Department of Materials Science and Metallurgy, University of Cambridge
Date
03/10/02
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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