Microstructural coarsening in dense binary systems

The kinetics of microstructural evolution driven by phase coarsening (Ostwald ripening) in a binary, two-phase system were studied systematically at ultra high volume fractions of the dispersed phase. Three-dimensional phase-field simulations and theoretical analysis are compared. Late-stage microstructure evolution at ultra high volume fractions ( V V > 0.9 ) are reported here. One interesting finding is that the scaling exponents, m , for the kinetics of phase coarsening at ultra high volume fractions take values in the range 2 < m < 3 , depending on the precise volume fraction of the dispersed phase, when varied over the narrow range 0.9 < V V < 1 . This result is confirmed by a comparative study of simulated microstructures and measurements of interfacial energy decay rates with theoretical coarsening analysis. Scaled particle-size distributions derived from simulations at ultra high volume fractions agree neither with Wagner’s 3D particle-size distribution for interface-reaction controlled phase coarsening, nor with Lifshitz and Slyozov’s particle-size distribution for diffusion-controlled phase coarsening. The research reported substantiates that the kinetics of microstructure evolution at ultra high volume fractions, approaching true grain growth, exhibits a varying blend of both interface reaction-controlled and volume diffusion-controlled phase coarsening.