Nine samples of Al2O3±30 wt.% TiC composites were prepared by hot-pressing the Al2O3 powder mixed with TiC particles. The
average sizes of the TiC particles used for preparing the nine samples were dierent with each other. Knoop hardness measurements
were conducted on these nine samples, respectively, in the indentation load range from 1.47 to 35.77 N. For each sample, the
measured Knoop hardness decreases with the increasing indentation load. The classical Meyer's power law and an empirical
equation proposed originally by BuÈckle were veri®ed to be suciently suitable for describing the observed load-dependence of the
measured hardness. Analysis based on Meyer's law can not provide any useful information about the cause of the observed ISE
while true hardness values, which are load-independent, can be deduced from the BuÈckle's equation. It was found that the deduced
true hardness increases with the average size of TiC particles existing in the sample.