An analytical electron microscopic investigation of precipitation in an Al-Cu-Zn-Mg-Ag alloy.
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 degrees 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 CuAl2 although they contained a trace of silver. At peak hardness the microstructure consisted of the plate-like precipitates on (111)Al planes and theta' precipitates on (100)Al planes. Overaging resulted in the precipitation of equilibrium theta, CuAl2, which exhibited a lath morphology and an orientation-relationship with the matrix (210)Al magnitude of (110)gamma; (001)Al misoriented from (001)gamma by approximately 6 degrees. Prolonged overaging at 250 degrees C resulted in the formation of cuboid-shaped Al5(Cu,Zn)6Mg2 precipitates which had a cubic crystal structure and a cube:cube orientation-relationship with the matrix.
Manchester Materials Science Centre, University of Manchester/UMIST, Great Britain.
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F
Hasan
G W
GW
Lorimer
D000497:Alloys; D000535:Aluminum; D011232:Chemical Precipitation; D003300:Copper; D008274:Magnesium; D008854:Microscopy, Electron; D012834:Silver; D014961:X-Ray Diffraction; D015032:Zinc
D000497:Alloys; D012834:Silver; D003300:Copper; D000535:Aluminum; D008274:Magnesium; D015032:Zinc