Shimano TOURNEY FC-TY301 crank arm material I have spent ~30 minutes searching for a clue, maybe I'm getting old and dull...
Are the FC-TY301 crank arms made of steel or aluminium alloy?
The crank-arms are aluminium as of any Shimano cranks but the chain-rings in this case are steel. The axle is always steel.

If you have a unit at hand, it's easy to check with a magnet.

(Anyway, a magnet may be a useful item also in shop for a discrete test of a component or a metal frame for material.)