Less common alloyants include aluminum (Al), cobalt (Co), copper (Cu), cerium (Ce), niobium (Nb), titanium (Ti), tungsten (W), tin (Sn), zinc (Zn), lead (Pb), and zirconium (Zr).
To achieve these improved properties the metal may require specific heat treating, combined with strict cooling protocols.
Alloy steels from earlier times were expensive luxuries made on the model of "secret recipes" and forged into tools such as knives and swords.
Because of iron's ferromagnetic properties, some alloys find important applications where their responses to magnetism are valued, including in electric motors and in transformers.
The properties of steel depend on its microstructure: the arrangement of different phases, some harder, some with greater ductility.
TRIP steels typically require an isothermal hold at an intermediate temperature during cooling, which produces some bainite.
This produces islands of austenite surrounded by a matrix of softer ferrite, with regions of harder bainite and martensite.
The resulting product can absorb energy without fracturing, making it useful for auto parts such as bumpers and pillars.