The temperature and loading-time dependence of the Vickers microhardness of single crystals prepared by using the floating zone method were investigated at 25 to 1000C (figure 1) for loading times of 5 to 60s. A clear inflection point at 700C was seen in a plot of log hardness versus temperature. A series of straight lines with various slopes was obtained in plots of log hardness versus log loading time of all samples. As the temperature was above the inflection temperature, the present data confirmed a previous observation for single crystals that ∂lnHv/∂T ∝ ∂lnHv/∂lnt.

Temperature and Loading Time Dependence of Hardness of LaB6, YB6 and TiC Single Crystals. Chen, C.H., Xuan, Y., Otani, S.: Journal of Alloys and Compounds, 2003, 350[1-2], L4-6