Constitution

Abstract

This chapter describes the different constitutions or states of ferrous materials with respect to the ordering of the atoms. Above the boiling point, the atoms are in the gaseous state and they fly through space completely disordered and well apart. Between the boiling point and the solidification point, they move around in the liquid state and are still disordered, but close together. Below the solidification point, they are in the solid state and are ordered into crystals. Their movements are now limited to oscillating about fixed points in the crystal lattice. The atoms can have more than one type of arrangement in the crystalline state. A region that has the same ordering is known as a phase. Several phases may be present in a ferrous material, e.g. during a liquid/solid transition or as crystals with different types of ordering. The state is said to be homogeneous if only one phase is present and heterogeneous if there is more than one.