The "Chinese script" microstructure is an aluminum - iron - silicon compound that is typical of impure aluminum castings.
Specimen 5 is the same alloy, but heat treated.
|
Here we have an aluminum casting alloy containing 4.5%
copper and a maximum of 1.0% iron, 1.0% silicon, 0.3% manganese, and
0.3% zinc. The first photomicrograph was taken at 50X; the second
one was made at 200X. The etchant was Keller's etch. The "Chinese script" microstructure is an aluminum - iron - silicon compound that is typical of impure aluminum castings. |
|
The third phase, originally smoothly gold colored and now a
faint pink in the image at left, is CuAl2. Note the "brown rings"
that are due to coring. Specimen 5 is the same alloy, but heat treated. |