Composition: Cu-4%Sn.

Processing: Sand casting.

Etching: 1 min immersion in FeCl₃ alcoholic solution.

Typical radial structure of cast metals with equiaxial grains in the periphery and columnar ones in the central region. Grains of different tonality are visible with the naked eye. Sn segregation is clearly revealed in the micrographs, where some small particles of δ phase are often observed. This lack of compositional homogeneity in Sn distribution is due to its limited diffusion, resulting in a wide α+L field and the large solidification range (>100ºC). 

Cu-Sn diagram

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