Phase Diagrams

· The distribution of the α- and CuAl₂ phases produced by the slow cooling is shown opposite.
· The θ-precipitates do not inhibit the motion of dislocations very much and the material is ductile and has a low work hardening rate.
· Non-equilibrium cooling causes formation of the finer precipitate structure shown in the lower diagram.
· These fine θ-precipitates hinder the motion of dislocations, causing a higher yield stress and work hardening rate than that of the slowly cooled material.

From: Ashby & Jones, "Engineering Materials 2," Pergamon (1986)