4. Major families of industrial heat treatments

4.1 Annealing

Annealing, a slow cycle involving relatively high temperatures, can be considered for most metal alloys with different objectives:

• a - reduce chemical heterogeneities (different types of segregation) resulting from metal solidification. Given the conditions of diffusion in the solid phase, these anneals require prolonged hold times at relatively high temperatures: we typically aim for diffusion paths, for the element deemed too segregated, of the order of magnitude of the grain size, i.e. around fifty micrometers. Holding for several hours, at absolute temperatures of around 80% of melting temperature, leads to coarse structures that must then be refined by work-hardening and recrystallization, or by normalization(s) in the...