6082 t6 https://www.makeitfrom.com/material-...82-T6-Aluminum

5083 O https://www.makeitfrom.com/material-...083-O-Aluminum

However for armour for a feather HDPE is the go too as it is cheap, eat up energy (look at Gabriel vs Carbide) light and way easier to build with.

metals, Ti is also a good choice if you got the money and the stronger grade Au also is useful (7075 or 2024) if used in a corret manner. HARDOX is great if can get into your weight budget