Diffusion in metals

Diffusion in metals is an important chapter in Metallurgy-Physics: it is the very basis of the macroscopic phenomena observed at the end of a heat treatment to improve volume or surface properties (by surface treatment) and, in general, it controls the evolution of a material as soon as time and temperature intervene.

Diffusion was initially observed on simple cases to understand the mechanisms at the level of the crystal lattice and to determine the physical parameters that characterize it (diffusion coefficients, activation energies, frequency factors).

Today, numerical values for many systems (pure metal, impurities in a pure metal, binary alloys, ternary alloys, etc.) enable us to understand the possible and existing applications of this research in fields such as sintering, surface treatments, welding and corrosion: knowing the diffusion constants, we can already predict heat treatment times and temperatures in simple cases (carburizing steels, for example).

However, in practice, the parameters involved are often multiple: for example, in a welding operation, to predict diffusion, you need to take into account the temperature gradient, the electric field, chemical affinities and the movement of the liquid metal. The aim of this article is therefore to separate the analysis of the various parameters in order to better understand their importance in transport phenomena.