|
The
thermodynamic process of trans-formation from one phase to another requires
the nucleation of the new phase and the growth of these nuclei to produce
the
final equilibrium state. Under ideal conditions these processes can take
place so that all path points are equilibrium states of the system. In
a real phase trans-formation, finite rates occur and the final micro-structure
may depend upon the temperature-time history of the system. Transformations
can be carried out under isothermal or constant cooling rate conditions,
or following a programmed time-temperature sequence. In addition, for certain
materials non-thermodynamic phase change processes can operate. The example
discussed is the martensitic transformation. |
|
|
