The Galaxy Alpha is not only the first metallic Samsung Android smartphone, it is also the slimmest Galaxy device ever made, and Samsung has explained in a blog post how it went about constructing the metal body which is used in the Galaxy Alpha. The post explains how the metal frame of the device is obtained by trimming a rough metal material, and is followed by creating spaces for things like the battery that are then attached to that metal frame. Samsung has also detailed how the different colors of the phone (blue, gold, black, silver, and white) are applied, and how the metal frame is then diamond cut to obtain the unique shape you see on the sides of the Galaxy Alpha.
It's a very interesting read of Samsung's design process for its first metallic Galaxy smartphone, so go ahead and take a look at the source link.