Grain refining in spark plasma sintering Al2O3 ceramics

•The nanostructured ceramics can be synthesized by using micro-sized starting powders, via a so-called grain refining effect.•The grain refining effect can only occur for the starting particle larger than a certain size.•The grain refining was explained by a thermo-mechanical fatigue effect.

The paper reports the effect of starting powder size and sintering temperature on the grain refining in spark plasma sintering Al2O3. It was found that the grain refining effect only occurred for the starting particles larger than a certain size. The grain size increased with increasing sintering temperature. The grain refining is likely caused by the rearrangement of dislocations through a thermo-mechanical fatigue process. It suggested that nanostructured alumina ceramics could be synthesized from micro-sized powders by optimizing the particle size and sintering temperature.