A method for estimating the grain size of a newly formed phase is presented for isothermal and continuous cooling transformations in which the new phase nucleates homogeneously, on the parent grain boundary surface or grain edges. In the isothermal transformation it is demonstrated that the grain size of the new phase depends only on the ratio of the nucleation rate to the growth rate and not on the individual values of nucleation or growth rates. It is also demonstrated that the grain size of the new phase is proportional to one half and two thirds the power of the parent grain size for grain surface and grain edge nucleations, respectively. In continuous cooling transformation, the grain size of the new phase depends on both nucleation and growth rates. When the ratio of the nucleation rate to the growth rate is independent of temperature, the grain size of new phase does not depend on the cooling rate. The grain size of the new phase in the process of transforming, or when more than two types of sites are active is also discussed. The results obtained in the present study are applicable to reactions where a parent phase transforms completely to a new phase, such as solidi~cation. recrystallization. massive and discontinuous transformations.
R&w&--Nous pr&entons une m&hode pour estimer la taille des grains d'une phase nouvellement form&e, pour des transformations isothermes ou en refroidissement continu dans lesquelles la nouvelle phase germe de man&e homogtne sur Ia surface des joints de grains ou sur les arites des grains de