There are two specimens here; the one at left has been exposed to high temperatures but is still OK; the one in the photomicrograph below was overheated.
What differences in microstructure do you see ?
OK to look at the answer below now.
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Nichrome (shown at left at 50X) is an alloy of 70% nickel
and 30% chromium, which is a face centered cubic (FCC) solid
solution. It is oxidation resistant (because the oxide scale is
adherent) and creep resistant (because of solid solution strengthening
of the nickel by the chromium). It also has a high electrical
resistivity because of the high alloy concentration. These
properties make nichrome useful for electric furnace heating elements. There are two specimens here; the one at left has been exposed to high temperatures but is still OK; the one in the photomicrograph below was overheated. |
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The image at left was also made at 50X. What differences in microstructure do you see ? OK to look at the answer below now.
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