Aluminium Bar is required to craft workstations such as the Recycler. It can be obtained by melting down 2x Aluminium Wire at the Melting Furnace.
The easiest way to find Aliminium Wire is to head to Bunker Alpha. If you’re lucky you’ll find them in crates. However they are more readily available from combat gear boxes purchased with yellow and red coupons.
Similar to Aluninium Wire, Bauxite can also be melted down in the Melting Furnace to produce Aluninium Bars. Mining iron ore nodes at Limestone Spires (Red Zone) will give a chance at rewarding Buxite.
Once you have the recycler you can also recycle canned food for a chance at getting Aluminium Bars. Feel free to eat them first, the empty cans will give the reward too.