ABSTRACT
Phase transformations play a key role in physical metallurgy, since most industrial alloys are subjected to some kind of heat treatment for the enhancement of their properties. Every alloy is made up of several phases, which are either solid solutions or intermetallic compounds. Heat treatment causes a change in the structure of the alloy through phase transformations. The most important effect of phase transformations is that they shape the microstructure and properties of metals and alloys. Several microstructural changes are caused by phase transformations: change of phase fractions and phase compositions, dissolution of some phases and precipitation of others, modification of the grain size, compositional segregation or homogenization, changes in dislocation density and other lattice defects, generation of new interfaces or modification of interfacial structure, generation of internal stresses and strains. Phase transformations are distinguished in diffusive and non-diffusive, depending on whether atomic diffusion is a prerequisite for the transformation to take place.
