Photomicrograph Database

Artifact ID BC 0613/0582
Negative Number NS106
Magnification 100x
Etchant K2Cr2O7, FeCl3
Photo Date 2/15/2000

Photomicrograph Description

Grains with annealing twins, nonmetallic inclusions, and heavy intergranular corrosion.




Post-casting treatment possible.

Metallographic Description

Dendritic structure with much interdendritic corrosion. The remaining solid dendrites have largely recrystallized and acquired twins. Remnants of "Chinese script" alpha+delta eutectoid can be seen. The grains are surrounded by a fringe or film of paler color; this may be beta (see Scott:14). Inside the grains are numerous round or oval globules, probably Pb. Twinned redeposited copper has occupied some of the corrosion voids. The composition is complex. A seam or fold in the metal was produced probably at the time of manufacture.

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