Spring comment:
Steel is an amazing alloy. Yes, it is an alloy of Iron and carbon.
Because you can change it's properties through controlling the temperature you can make it into amazing things like springs. People who do this use terms like "Spring tension" which leads to terms like "relaxing the metal" (removing tension ya know)
I teach a class in metal working and part of the class is taking three pieces of 1050 Steel (most common antique hardenable steel alloy) and do the following:
Piece 1: Heat to orange color, then put into a bucket of fine sand
Piece 2: Heat to orange color, then quench in water.
Piece 3: Heat to orange color, quench, then reheat to dull cherry color, then re-quench in water.
After about 15 minutes (to let the sand quenched bit cool) we take out all three and try to fold them in half.
Piece 1: Folds easily and retains the bend when released
Piece 2: Breaks/Shatters when bent too far(sounds like glass when it does)
Piece 3: Bends and then springs back to it's original shape.
NOTE: Copper and Brass are the exact opposite of steel. Heating and quenching it softens the metal, while heating it and letting it cool slowly hardens it. (can make brass brittle enough to snap when bent)