Chapter 12 – Steel Transformations

The wide variety of steels stems from the various stable phases in the iron–carbon phase diagram including austenite, ferrite and pearlite, as well as the occurrence of metastable martensite and bainite upon rapid cooling from the austenite phase field. The crystallography and formation mechanism of these phases, and the kinetics and effect of alloying elements on the transformation between them, are discussed in detail. The strength and brittleness of steels depend on the martensite content and their hardenability can be determined by Jominy end-quench tests. Steels can be subjected to a range of thermo-mechanical treatments to improve their properties. A few non-ferrous alloys also exhibit the martensitic transformation and when this happens, they may also exhibit the shape memory effect.