Gallery 3
Alan Stone
The director of Aston Metallurgical Services in Wheeling, Ill., ALAN
STONE, makes his living by helping clients solve their metal-related
problems. One such problem is "metal dusting," a situation in industrial
settings in which the surfaces of furnace tubes, processing tubes, and
other metal components turn to dust, sometimes with catastrophic
results.
Images 1 and 2 in this gallery depict some microscale signs of metal
dusting in a furnace tube. Image 3 shows a weld joining two pieces of
copper tubing. The individual grains of the metal on each side of the
weld are visible as irregular shapes with thin boundaries. Image 4 shows
the mix of phases that form when ductile iron is hardened through a
hot-flame process. Images 5 and 6 reveal the dendritic, or branched,
grains of an ancient bronze arrowhead that Stone bought but couldn't
help cutting up to examine metallographically. Dendritic grains form in
some cast metals as they solidify from the melted state. The final
three images, 7–9, are from metal that made its way from outer
space to Earth in three different meteorites and finally into Stone's
hands.
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