Particle‐Inhibited Grain Growth in AI 2 O 3 ‐SiC: I, Experimental Results

An extensive experimental study has been conducted to examine the influence of ultraflne SiC particles on grain growth in A1 2 O 3 . 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 A1 2 O 3 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, φ, has been measured as a function of annealing time, particle volume fraction, and annealing temperature. φ 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 φ 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.