Dear list,
I’m looking at the microstructures of the copper-base alloys that I
studied for my PhD and two fundamental questions came up concerning the
bronzes:
1. What do elongated inclusions tell us about the treatment of the metal?
If for examples lead inclusions are elongated in the metal in the line of
working. Are they then the result of hot working the metal, or can they
also be stretched by just cold working? Is there any means of seeing the
difference?
2. The second question is about the presence of the alpha-delta eutectoid
in bronze. I know that it can appear from 8-10% of tin onwards. I have 2
samples which are completely made of this intermetallic phase (mirror
which have nicely published reference material among Roman and Chinese
mirrors) so they do not pose a real problem. The EDX gave a tin value of
around 30%, which is somewhat on the high side (should be around 27-28)
but seen the semi-quantitative nature of EDX they are acceptable. But then
I have a whole series of samples with around 20% of tin and I cannot see
the eutectoid there. On the one hand the EDX seems to be rather reliable
so the 20% value should be ok, but on the other hand I do not know if the
eutectoid could be removed by annealing. So the tin of the intermetallic
phase is reabsorbed in the copper, leaving a more ore less uniform alloy
in solid solution. The phase diagram of copper and tin is rather complex
and I do not seem to understand this. Did any of you encounter any
problems with the Sn values when doing SEM-EDX analyses? I for example
noticed that the tin values are elevated when Zn is present. Maybe the
matrix effect also influences the data when a certain amount of tin is
present and gives a too high value.
I would be very grateful if any of you could just tell me
something/anything on this matter.
Many thanks in advance,
Parsival
---------------------------------------
DELRUE Parsival
PhD student Archaeometallurgy
[log in to unmask]
GHENT UNIVERSITY
Research Unit Near Eastern Archaeology
St-Pietersplein 6
B-9000 Gent - Belgium
http://www.neareast.ugent.be/
|