Apple just announced that the new iMac was made possible by an obscure metal joining process called Friction Stir Welding. Invented in 1991, friction stir welding “works by mechanically intermixing the two pieces of metal at the place of the join, transforming them into a softened state that allows the metal to be fused using mechanical pressure, much like joining clay [or] dough.” It’s different from normal welding in that the metal doesn’t melt, so it’s good “for applications where the original metal characteristics must remain unchanged as much as possible.”
The Welding Institute near Cambridge, UK, invented this welding method and holds the patent on the process. It’s not known what sort of licensing fee Apple is paying in order to use the process.