is an intermetallic compound between the two elements. It is the thermodynamically
stable precipitate formed when an alloy such as Al- 4wt% Cu is slowly cooled
from the single solid solution a-phase
to room temperature. The compound can exist over a small range of compositions
about stoichiometric and exhibits congruent melting at about 600 C.
In overaged precipitation hardened Cu-Al alloys, CuAl2 is the precipitate that provides the material hardening. The precipitate has incoherent boundaries with the (Al) matrix and consequently the interaction with dislocations is reduced compared to non-equilibrium precipitates with coherent boundaries with the matrix.
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