1. Microstructural behavior of Copper Alloys
Engr 45 Fall-05
By: Marco Ruiz
Justin Matari
Jeremy Romano

2. What we did…
We casted several different combinations of copper alloys.
Our objective is to observe how different microstructures can effect these alloys.

3. Like Dissolves Like
To obtain a fully dissolved solid solution there needs to be some sort of compatible relationship between a solute and a solvent.
Knowing the structural similarities between the two elements we are able to predict whether one will dissolve into the other.

4. Question?
What happens when you attempt to dissolve two different microstructures?
This experiment will demonstrate the behaviors of common alloys: brass, bronze, copper-silver.

5. Warning
Metal gets hot
Use appropriate protection
Well ventilated area

6. Casting
Attempted to cast alloys into a pure calcium mold.
Failed

7. Casting (back up plan)

8. Alloy combinations Sample 1 Sample 2 Sample 3 Sample 4 Sample 5
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
%Cu
100 85 60
7.5
%Ag - 15 40
92.5
%Zn
%Sn
Hard
Rh  43
Rh 66 
Rh 71
Rb 44 * 
Rh 55

9. Zero to low alloy Copper 925 silver
Rh Rh Even distribution of grains

10. High Alloy (fcc structure)
60 Cu-Ag Cu-Ag 15
Rh Rh 66
Both are completely soluble no matter what %.

11. Ag-Cu Phase diagram

12. Sn (fct), Zn (hcp) 85 Cu-Sn 15 85 Cu-Zn 15 Rb ? Rb 44
Grains act as barricades, non-uniform dist.
What a difference!!!

13. Sn-Cu Phase diagram

14. Zn-Cu Phase diagram

15. 60 Cu-Sn 40 Solubility limit has been reached Unlike microstructures
Extremely brittle

16. 60 Cu-Zn 40 Not annealed Extremely hard
Solubility limit has not been reached

17. Discussion
Like solvents, not all molten metals are fully miscible with each other.
Copper and zinc ions are about the same size, so except for the electric charge, they are pretty much the same so far as the crystal is concerned……
Copper ions harden silver by the size of the atom. Smaller copper ions cause interstituals in the silver. But, they do not harden copper nearly as much as tin or zinc.