Kinetics and Microstructural Control
Microstructural Development

· Stages in the precipitation process follow. The initial state shown is a random solid solution of copper in the aluminum matrix.

· In this condition the copper atoms substitute randomly for aluminum within the fcc structure of the aluminum crystal. 
· The alloy is dilute and not all unit cells will contain an impurity atom. 
From: Ashby & Jones, "Engineering Materials 2," Pergamon (1986)