Most hot (ungrounded) conductors are under a brass or copper colored screw which may be made of a different metal than the white or silvery colored screw the neutrals are under they may be diferent metals and or have a different coeficient of expantion as in the theory of the bimetalic thermostat or motor heater bimetalic trip unit. Now it is my understanding that the actual damage occurs when the screw doesnt expand as quickly as the aluminum causing it to be compressed more and squeeze out the sides a little bit yet when it cools down the aluminum cannot squeeze its self back to a tight connection against the screw so the thinking would be that al has a high coeficient of expantion and a metal whoch has a lesser value of expansion would most likely be the problematic one. That is my best guess. BTW it has been my experience that the al problems are almost always close to the panel as this is where the highest current occurs in the branch. GO GIANTS NICE WIN!!!
