Composition: Cu-37%Zn.

Processing: Sand casting.

Etching:  30 s immersion in FeCl₃ alcoholic solution.

The Zn content in this brass corresponds to the peritectic region where all the liquid phase is consumed (see the Cu-Zn phase diagram). As shown in the macrograph,  columnar grains are revealed after etching  These grains show a substructure consisting of a dendritic skeleton of α primary phase (solid solution of Zn in Cu). This phase shows Zn segregation, which can be revealed by secondary etching with a mixture of ammonia and hydrogen peroxide (not shown here).

The β phase that results from peritectic reaction between the liquid and the α phase appears dark at the interdendritic spaces. It is worth noticing that the initially round edges of the primary α phase acquire angular shapes due to preferential reaction of specific crystallographic planes.

Cu-Zn diagram

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