Effect of Second‐Phase Particles on Grain Growth in Calcite

Grain growth in polycrystalline caicite (CaCO 3 ) at 800°C and 300‐MPa confining pressure is inhibited by the addition of Al 2 O 3 particles; volume fractions of second phase (f) ranged from 0.02 to 10.0 vol%, and several powders with different average particle size were used. The stable grain size reached during heat treatment was inversely proportional to l/f m where m varied from 0.3 to 0.55 — agreeing with results from other grain growth experiments in ceramics and metals, and with models developed for particles located at grain boundaries and grain corners, but not agreeing with models developed for random dispersions. The dependence of the stable grain size on second‐phase particle size in these experiments was less systematic, possibly because of variations in the particle size distributions used, or because of particle agglomeration effects. In the single‐phase aggregates, the growth kinetics were consistent with a normal grain growth equation with n=3, although uncertainties were large.