Computer Simulation of Grain Growth and Ostwald Ripening in Alumina—Zirconia Two‐Phase Composites

Abstract

The kinetics of grain growth and Ostwald ripening in Al2O3‐ZrO2 two‐phase composites was systematically investigated using two‐dimensional (2‐D) computer simulations, based on a diffuse‐interface field model. Using average values for the experimentally measured ratios of the grain boundary energies to the interphase boundary energy as the input, the predicted 2‐D microstructural features and their evolution are in excellent qualitative agreement with experimental observations on 2‐D cross sections of 3‐D Al2O3‐ZrO2 two‐phase composite microstructures. It was found that the coupled grain growth in Al2O3‐ZrO2 composites is controlled by long‐range diffusion and the average size (Rt) as a function of time (t) follows the power‐growth law, Rmt ‐ Rm0=kt with m= 3, which is independent of the initial microstructures and volume fractions of the two phases. The predicted variation of the kinetic coefficient (k) on the volume fraction follows a trend similar to that experimentally measured through the entire range of volume fractions. The scaling of grain size distributions is observed at a given volume fraction, i.e., they are time‐invariant in the steady state. However, the characteristics of size distributions vary with the initial microstructures and the volume fractions. The relationship between matrix grain size and second‐phase grain size is discussed.