Aluminium, Titanium and Steel are the popular material used in FPV drone hardware. The weight differences are fairly significant actually. Steel is the heaviest for a reason, they are tough, but even steel has many grades.

• Nylon 6mm big 6mm 0.0943g
• Nylon 6mm small 8mm 0.0616g
• 7075 aluminum 6mm 0.1674g
• 7075 aluminum 8mm 0.2034g
• Titanium 6mm 0.2623g
• Titanium 8mm 0.3590g
• Stainless 6mm 0.4688g
• Stainless 8mm 0.5454g
• Steel 10-9 button 6mm 0.5209g
• Steel 12-9 cap 6mm 0.6479g

Personally, for extreme weight saving, I’d put aluminium all over the quad where strength doesn’t matter. But for motors, I’d stick with steel.