ParticleaInhibited Grain Growth in AI2O3aSiC: I, Experimental Results

An extensive experimental study has been conducted to examine the influence of ultraflne SiC particles on grain growth in A12O3. Grain growth has been studied as a function of annealing time, particle volume fraction, and annealing temperature. The SiC particles reduce the grain-growth rate of A12O3 by >3 orders of magnitude, resulting in final grain sizes that decrease with increasing particle volume fraction. The fraction of SiC particles on grain boundaries, phi , has been measured as a function of annealing time, particle volume fraction, and annealing temperature. phi decreases during grain-growth anneals, implying that grain boundaries are able to break free from particles and this is true to a greater extent for smaller volume fractions of particles. Further, it has been discovered that phi and average grain size, G, are strongly correlated, such that any increase in G results in a predictable decrease in pH. This new finding has revealed a path for microstructure development in this system that proves to be critical in the equilibrium and kinetic analyses described in a companion paper.