Steel is stronger; aluminum is (much) lighter--and still pretty strong.
Steel is stronger and weighs more. Aluminum road bikes are super vibrated and it can hurt your hands and cause carpal tunnel (carbon fork and handle bars dampen it). Anyone who has rode a carbon fiber bike knows that its the upgrade from steel. Steel however, is effected by gravity differently in comparison to aluminum. Gravity pushes down on your steel frame on long descents that it actually causes the frame to flex under the force. Here's a way to put it, Aluminum feels dead and steel feels more lively because it isn't as ridgid. A really cool benefit to a steel frame is if you get in a crash and damage it you can have it fixed easily compared to aluminum and especially to Carbon Fiber
Steel:
Titanium
Scandium frames don't exist. It's a marketing ploy.
What does exist is aluminium alloyed with scandium.
The functional difference between an aluminium alloy containing scandium vs plenty of other aluminium-based alloys is marginal-to-none.
Carbon fiber
Bicycle frames are made of alloys, carbon fiber, steel, titanium, or bamboo.
Titanium
Titanium
zinc, steel, titanium, scandium, aluminum, wood, plastic
Titanium Steel is the strongest.
Either steel, aluminum, or titanium.
The most common metal used for standard bicycle frames is steel, although it is possible to get frames made from graphite, aluminum, and titanium alloy.
Steel Aluminium Carbon Fibre Titanium.
I believe Aluminium = 2.7, and Carbon Steel = 7.85
Steel is made from iron. We combine a small amount of carbon with iron to get (make) steel.
Usually Cr-Mo, Chrome-Molybdenium steel. But aluminium and even Titanium can/have been used.
You bond steel and titanium by melting iron and titanium together. And putting the mixture in a furnace then use the thing that blows air into a fire on the furnace to blow air into the mixture. That blows most of the carbon out of the mixture thus hardening the mixture and making it a steel and titanium mixture.