1. Metallic material: microstructure and metallic character

1.1 Microstructure

• The metal material is a polycrystalline composite

  A metal part is made up of an assembly of crystals, each of which is the periodic repetition (lattice) of a "pattern" of atoms in three directions in space: a crystal is the infinite stacking of a single mesh defined by the pattern and the lattice's three elementary translation vectors. If all the atoms are identical (pure metal), the crystals are all identical (a single phase): the whole is a single-phase polycrystal (figure 1 ).

  In the case of a metal alloy, several species of atoms are present, and there may be identical crystals (e.g. primary solid solution...