Composition: Cu-10.5%P (hypereutectic).

Processing: Sand casting.

Etching: 30 s immersion in FeCl₃ aqueous solution.

A radial structure typical of casting is visible in the macrograph. In a hypereutectic Cu-P alloy such as this one, there are dendrites of primary Cu₃P. This is phase has a fixed composition and, therefore, does not show segregation after etching. Similarly to X5 and X6 specimens, the liquid transforms into a eutectic aggregate upon cooling. The eutectic consistes of lamellas of α and Cu₃P phases.

The micrographs reveal eutectic colonies with regular or irregular arrangements of the lamellas depending on the sectioning plane. An aditional feature of this specimen is the α halo surrounding the Cu₃P dendrites.

Cu-P diagram

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