Load-dependence of Knoop hardness of Al2O3-TiC composites

Nine samples of Al2O3-30 wt% TiC composites were prepared by hot-pressing Al2O3 powder mixed with TiC particles. Different sizes of TiC particles were used for preparing the nine samples. Knoop hardness measurements were conducted on these samples in the indentation load range from 1.47 to 35.77 N. For each sample, the measured Knoop hardness decreased with increasing indentation load. The classical Meyer's power law and an empirical equation proposed originally by Buckle were verified to be sufficiently suitable for describing the observed load dependence of the measured hardness. Analysis based on Meyer's law cannot provide any useful information about the cause of the observed ISE while true hardness values, which are load independent, can be deduced from the Buckles equation. It was found that the deduced true hardness increases with the average size of TiC particles existing in the sample. 19 refs.