This is what I call a "full tang" axe. The axe head and haft are all one continuous piece of 7075-T6 Aluminum. The haft is skeletal, i.e. areas of solid metal have been removed to reduce weight while retaining structural integrity.
Two pieces of poplar are glued and pinned to either side of the aluminum haft to create the illusion of a normal axe handle.
The overall effect is a pretty convincing and very sturdy aluminum axe with a low weight and excellent balance. Because the core of the haft is aluminum, you can meet an aluminum blade with it "edge to edge". That core of aluminum is visible up and down the length of the handle, but it could certainly be painted to match the rest of the haft.