An analytical electron microscopic investigation of precipitation in an Al-Cu-Zn-Mg-Ag alloy

✍ Scribed by F. Hasan; G. W. Lorimer

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 787 KB
• Volume: 24
• Category: Article
• ISSN: 1059-910X
• DOI: 10.1002/jemt.1070240409

✦ Synopsis

Abstract

The distribution, morphology, chemistry, and crystallography of the precipitates formed during aging of an Al‐Cu‐Zn‐Mg‐Ag alloy have been studied using analytical transmission electron microscopy. The first precipitates to appear during aging at 150°C were thin hexagonal‐shaped plate‐like precipitates which formed on the {111}~Al~ planes. These precipitates had a face‐centred orthorhombic crystal structure and their composition was essentially CuAl~2~ although they contained a trace of silver. At peak hardness the microstructure consisted of the plate‐like precipitates on {111}~Al~ planes and θ′ precipitates on {100}~Al~ planes. Overaging resulted in the precipitation of equilibrium θ, CuAl~2~, which exhibited a lath morphology and an orientation‐relationship with the matrix (210)~Al~ ∥(110)~γ~; (001)~Al~ misorlented from (001)~γ~ by ∼6°. Prolonged overaging at 250°C resulted in the formation of cuboid‐shaped Al~5~(Cu,Zn)~6~Mg~2~ precipitates which had a cubic crystal structure and a cube:cube orientation‐relationship with the matrix. © 1993 Wiley‐Liss, Inc.