Phase Diagrams

· A typical commercial alloy may have the average composition Al - 4 wt % Cu. The diagram shows the pseudo-binary diagram and a cooling path for this alloy.
· At the starting temperature (560 C) the material is a polycrystalline single phase material (here κ is called α!). As its temperature is reduced, the composition line crosses the solubility limit curve (solvus line) and the CuAl₂ phase is precipitated.

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

· In thermodynamic equilibrium, the cooling process will precipitate the
θ-phase at grain boundaries.