Kinetics and Microstructure 
Table of Contents



   Phase Nucleation
      Heterogeneous Nucleation

   Transformation Rate

   Isothermal Transformations
      Martensitic Transformation

   C-C-T Curves

   Precipitation Hardening
      Microstructural Processes

   Design Issues
      Chrome-Moly Steel
      Skin of Concorde

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.