Yes, they are aluminum. It is possible to press ball joints in and out of the aluminum arms, if you really know what you are doing. That said, I recommend against trying it. You could warp the arm, or cause it to crack around the joint, later and unexpectedly.
The answer I was looking for.
Useful information is what I try to give and its what I seek.
That being said, I purchased new UCA's for the rear.