Alloys
Alloys are a mixture of two or more elements, normally with one element being the major constituent. In a bicycle ferrous or light alloys are used for the frame, and the majority of the mechanical components (chain, bearings, etc.) will also be made from metal alloys.

The diagram shows stress/strain curves for a series of carbon steel alloys. The '% carbon' is the amount of carbon added to the iron matrix of the alloy, the maximum value in this group being 1%. The data shows that Young's modulus is independent of the alloy content, but the yield stress (the stress at which plastic deformation starts) increases as the carbon content increases. Since the material will be used in its elastic range, this observation indicates that the higher carbon content material can give a wider operating range. The disadvantage of adding more carbon is that the material tends to become more brittle and less able to adsorb energy before fracture.

From: Hibbeler, "Statics and Mechanics of Materials," Macmillan (1993)