11. Anisothermal precipitation

In most precipitation studies, precipitation is analyzed along isothermal paths. In practice, however, a significant proportion of the thermal or thermo-mechanical paths are anisothermal, which has important implications for precipitation paths and associated kinetics.

If we consider the various stages of conventional heat treatment, the anisothermal character is already present during quenching from solution temperature. However, as soon as the parts to be treated are massive, quenching can no longer be considered perfect, and precipitation can take place, during cooling, under very anisothermal conditions.

Secondly, the precipitation treatment itself can be anisothermal:

• or by accident (a solid part cannot be heated infinitely quickly);

• or deliberate, using...