About the Coarsening Model

This section or topic is specific to Console Mode.

The model is based on LSW theory (after Lifshitz and Slyozov (1961)1 Lifshitz, I.M., and V.V. Slyozov. 1961. “The Kinetics of Precipitation from Supersaturated Solid Solutions.” Journal of Physics and Chemistry of Solids 19 (1–2): 35–50. and Wagner (1967)2 Wagner, Carl. 1967. “Theorie Der Alterung von Niederschlägen Durch Umlösen (Ostwald-Reifung).” Berichte Der Bunsengesellschaft Für Physikalische Chemie 65 (7–8): 581–91. . The model is also described in Gustafson, Höglund, and Ågren (1998)3 'Simulation of carbo-nitride coarsening in multicomponent Cr-steels for high temperature applications'. In Advanced heat resistant steels for power generation (San Sebastian, Spain 27/04/1998 and Björklund, Donaghey, and Hillert (1972)4 Björklund, Stig, L F Donaghey, and Mats Hillert. 1972. “The Effect of Alloying Elements on the Rate of Ostwald Ripening of Cementite in Steel.” Acta Metallurgica 20 (7): 867–74. .

LSW theory is strictly only valid for low volume fractions of the particle phase. The theory predicts that the normalized particle size distribution obtains a constant shape where the largest particles have a radius equal to 1.5 times the average particle radius.

The calculations are performed in one cell on a maximum size particle which thus is assumed to be 1.5 times the size of the average particle size. The matrix phase is on one side in contact with the maximum size particle and on the other the matrix phase is in local equilibrium with an average sized particle. The effect of the surface energy is such that both the maximum size particle as well as the matrix phase grows.

The model allows you to perform coarsening simulations. You must explicitly set the DICTRA module to use this model with the command COARSENING_MODEL.

To use this mode, configure the calculation as follows:

• Have one cell only, with a single particle that is 1.5 times larger than the average particle size.
• The matrix phase should be in contact with the maximum size particle on the left/lower side, and then the model specifies a local equilibrium with an average sized particle on the right/upper side.
• The surface energy then results in growth of both the maximum size particle and the matrix phase. Use the SET_SURFACE_TENSION command to enter the surface energy to enable coarsening.