There's a reason that Shimano 24mm axles are made of steel. They are just not strong enough. Dub axles at 29mm can be aluminum but of course they are much bigger and therefore stronger.
Hambini did a video on this and argued that it can be done if the wall
Thickness is thick enough and the aluminium grain structure is consistent enough. However you still have the problem of steel bearings wearing on the axle as it happens with all aluminium crank spindles over time. And then I wonder just how much of a weight advantage there’s left if you built an aluminium crank spindle sturdy enough in 24mm. I think there’s also a reason why until now every aluminium spindle was oversized, BB30 or DUB. Same reason why aluminium bike frames are oversized when compared to steel. Stiffness to weight qualities of aluminium just work better that way.
