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Full Record for Micrograph 56

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Micrograph no
56
Brief description
Al 96, Cu 4 (wt%), solution treated and overaged - precipitation hardening
Keywords
alloy Link to MATTER Glossary entry for alloy, aluminium Link to MATTER Glossary entry for aluminium, copper, metal, metastable Link to MATTER Glossary entry for metastable, overaged Link to MATTER Glossary entry for overaged, precipitation Link to MATTER Glossary entry for precipitation, precipitation hardening Link to MATTER Glossary entry for precipitation hardening, quenching Link to MATTER Glossary entry for quenching, solution heat treatment Link to MATTER Glossary entry for solution heat treatment
Categories
Metal or alloy
System
Al-Cu   Link to phase diagram
Composition
Al 96, Cu 4 (wt%)
Standard codes
Reaction
Processing
Solution treated and over-aged
Applications
Sample preparation
Technique
Reflected light microscopy
Length bar
200 μm
Further information
This sample has been aged after quenching to enable the growth of precipitates from a supersaturated solid solution. The strength of the alloy has been greatly improved by precipitation hardening. A precipitation sequence is observed eventually resulting in the formation of the stable θ phase through a series of metastable intermediates. The θ phase is an intermetallic compound with a composition close to CuAl2. The θ precipitates preferentially form on Al grain boundaries, as these are excellent heterogeneous nucleation sites. The depletion of Cu near the boundaries to these precipitates is one reason for the formation of adjacent precipitation free zones (PFZ).
Contributor
Prof T W Clyne
Organisation
Department of Materials Science and Metallurgy, University of Cambridge
Date
25/10/01
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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