Dislocations and mechanical properties of single crystal niobium disilicide

The mechanical properties of single crystal NbSi{sub 2} have been investigated along [0001] and 45{degree} from [0001] toward [11{bar 2}0] using a Nikon QM-2 hot hardness tester from room temperature to 900 C in vacuum. The hardness along [0001] increases from room temperature to 300 C followed by a sharp decrease in hardness with temperature which is accompanied by a large uplift observed surrounding the indentations. Dislocations surrounding the indentations at room temperature and 300 C were analyzed using techniques in transmission electron microscopy to find slip by <10{bar 1}0> dislocations at room temperature with a change in the active slip systems at 300 C. The hardness along a direction 45{degree} from [0001] toward [11{bar 2}0] sharply decreases with increasing temperature above room temperature. Coarse slip lines surround the indentations referring to slip on the basal plane