Grain Growth in Two‐Phase Ceramics: Al ₂ O ₃ Inclusions in ZrO

The effect of Al 2 O 3 inclusions with a greater average size (0.6 μm) than the average particle size of the major phase powder (<0.1 μm) on grain gowth was examined by sintering ZrO 2 /Al 2 O 3 composites (0,3,5,10, and 20 vol%) at 1400°C and then heat‐treating at temperatures up to 1700°C. Normal grain growth was observed for all conditions. The inclusions appeared to have no effect on grain growth until the ZrO 2 grain size was ∼1.5 times the average inclusion size. Grain growth inhibition increased with volume fraction of the Al 2 O 3 inclusion phase. At temperatures 1600°C, the inclusions were relatively immobile and most were located within the ZrO 2 grains for volume fractions <0.20; at higher temperatures, the inclusions could move with the grain boundary to coalesce. Grain growth was less inhilited when the inclusions could move with the boundaries, resulting in a larger increase in grain size than observed at lower temperatures. Analogies between mobile voids, entrapped within grain at lower temperature due to abnormal grain growth during the last state of sintering, and the observations concerning the mobile inclusions are made suggesting that grain‐boundary movement can “sweep” voids to grain boundaries and eventually of four‐grain junctions, where they are more likely to disappear by mass transport.