Submitted by curator on Fri, 10/16/2015 - 13:59
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Inv. 31-52-272
Irregular clump of square wire
A complete section across one end; magnification, 200x [left and right]
Etchant: for micrograph on left, Klemms III; for micrograph on right, Ammonium hydroxide + hydrogen peroxide
(Sn, <0.009%; As, 0.68%; Ni, 0.20%)
The microstructure consists of polyhedral grains that, in their twinning and minimal distortion, are indicative of an annealing treatment after an only light amount of cold-working (left micrograph). Variously sized, scallop-shaped inclusions are dispersed unevenly throughout the interior of the metal, and most likely are remnants of non-metallic material (matte) that became entrapped in the copper during its original smelting (right micrograph).
Microhardness VHN: 107 ± 12 (n=5)
Uniform; data scatter (with the VHN ranging 118 to 85) seems to be a genuine record of variation in grain size within the wire, consistent with the working needed to thin its metal being heavier close to the surface.
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