Coarsening in Multicomponent Multiphase Systems [Final Report, November 1, 1995--October 31, 1998]

The goal of the project was to extend the theory of particle coarsening, which is well established for binary systems, to the case of multicomponent and multiphase alloys. The theoretical approach involved three stages: (1) a mean field description based on the Lifshitz-Slyozov-Wagner (LSW) [1,2] formulation (recently published in Acta Mater. [3]), (2) an analytical description of coarsening valid at small volume fractions where the Marqusee and Ross [4] model was employed and (3) a numerical simulation of three phase coarsening where the boundary integral method of Akaiwa and Voorhees [5] was implemented. The main result of the mean field analysis can be stated as follows. The growth rate of a particle from a particular phase in a multiphase system is precisely the same as that derived for a single phase, multicomponent system. Also, it was found that the scaled particle size distribution for each phase in the system has exactly the same form as that originally derived by LSW. Since it neglects particle interactions, the mean field theory is clearly unrealistic and as such the formulation of coarsening in low volume fraction multiphase systems was undertaken