What is the metallic alloy used in camera cases?
They are manufatured by what process?
In mass production complex shapes like that are usually cast, then the casting is machined where accuracy and good finish is required. Magnesium is a good candidate for casting and Googling around about cast camera casings it seems many if not most of them use magnesium.
This is the Samsung NX1 which is magnesium. https://en.wikipedia.org/wiki/Magnesium_alloy
Huh. Apparently magnesium is even lighter than aluminum. I did not know that.