3. Metal bases

The properties of steels depend on a number of factors: their crystallographic structure, i.e. the phases present, but also the content of interstitial or substitutional elements in these phases, and finally the size effect of the constituents. The nature of the phases, their proportion and size depend on the phase transformation conditions, which are also a function of the chemical composition. Other important phenomena include recrystallization after deformation and precipitation.

These complex interactions make it unreasonable to rely on simple, linear relationships between properties and chemical composition; nevertheless, such relationships are sometimes used to set orders of magnitude. It is therefore necessary to approach the influence of elements through two factors: the structural effect and the effect of composition, even if it is the overall effect that...