Composition: Hypoeutectic alloy Cu-4,5%P.

Processing: Sand casting.

Etching: Immersion in aqueous FeCl₃ solution during 40 s.

Cooling of this hypoeutectic alloy from the molten state produces primary α (a solid solution of P in Cu) dendrites and a lamellar eutectic aggregate consisting of α and Cu₃P phases. During etching the surface darkens relatively quickly as the α dendrites turn into a brown color. Nevertheless, medium-size equiaxial grains can be observed in the macrostructure here presented. In the micrographs, the dendritic morphology of primary α is clearly visible, although globular shapes are sometimes observed depending on the way they cut the surface. Microsegregation within the dendrites is evident (less P in the center of the dendrites). As for the eutectic aggregate, it shows white Cu₃P and red/brown α  phase.

Cu-P diagram

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