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This silicon bronze has a particularly complex
microstructure. Those lines aren't scratches ... The image at left is at 50X magnification. |
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Here the magnification is 500X. The copper - silicon system is reproduced below. What is the history of this specimen ? |
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The copper - silicon system is
shown at left ... Think through the sequence of freezing of an alloy around 4-1/2% silicon. After spending no more than a few moments' time and without fretting if it seems like hard work, look here. |
| This is
obviously a casting; the alpha is cored, with crystallographically
oriented "strain markings" which are probably precipitates. There
are at least two peritectics, three peritectoids, and three eutectoids
in this phase diagram, which renders interpretation of the
microstructure rather difficult. The last metal to freeze could
contain even more than 10% silicon, so evidence of nearly every phase
in the above diagram could show up somewhere in the cast
microstructure.
Go on to Specimen 4. |