You'll also see nomenclature with aluminium relating to the hardness. "6061-T6" where the "T6" indicates hardness on (I believe) the Rockwell B scale

And the engineers here can speak to this more clearly than I, but the myriad of aluminium "blends" often relate to tradeoffs in strength vs. workability. I remember reading one of the 70** series alloys is pretty strong but doesn't weld easily or well, hence it's used a lot for chainrings and other parts that can be stamped, etc.

Carbon Fibre always fascinates me in that it's so strong and light yet so vulnerable to catastrophic failure resulting from a relatively minor ding or scratch. Auto racing fans might remember some spectacular wrecks, especially in the late 80's early 90's when engineers were still figuring out the best way to align the sheets for impact protection. I'm still haunted by those pictures from F1 driver Martin Donnelly's 1990 career-ending shunt during practice for the Spanish Grand Prix at Jerez.