The Fe-C Phase Diagram

The interaction between iron and carbon is the basis of a large proportion of the quality of life that we enjoy today, for where would we be without steel? It was Dmitry Konstantinovich Tschernoff , who as a metallurgical engineer in Russia, discovered the critical temperatures of steel, published in 1868, the same year that Mendeleev published the periodic table, and Tolstoy wrote War and Peace.

The Fe-C equilibrium, however, is still uncertain in many ways, in part because of the many allotropic forms of iron and carbon, but also because the compounds they form are manifold. Some, for example, consider what we normally call `transition carbides’ as forming an equilibrium with ferrite, making them more stable than cementite which is in contact with ferrite. And is it reasonable to always think of ferrite as body-centred cubic? Is graphite always more stable than cementite? What of the Fe-100%C phase diagram?

These, and many other interesting and sometimes unsettled issues about what is probably the best-known phase diagram ever produced, will be addressed.