Periodic Table will give you the Atomic weight of Aluminum(Al-13) and Iron (Fe-26)
Carbon is an Element too . (C-6) but the fiber is in a composite with epoxy and that is a chemical not an elemental Material .

Strip down the various Bikes to their bare frames and weigh them if the answer really matters to you

Or get a Cubic Block of the identical size of the 3 different materials and weigh that .


Yes , Plus.. a Low cost alloy of either Aluminum or Steel has a Lower tensile strength

than A Higher tensile strength alloy, which costs More, But you can use less to get a similar strength Product.