| Popis: |
In order to analyse the results of bending strength measurements on neutron-irradiated samples of Al2O3, A1N and SiC, fracture toughness measurements were additionally conducted. The neutron fluences concerned were mostly in the range of 0.6 to 3.2 × 1026 n/m2 at irradiation temperatures of 400 to 550°C. A fracture toughness decrease was generally observed for polycrystalline materials which, however, was considerably smaller than the reduction of the fracture strength. Exceptional increase of the fracture toughness seems typical for the effect of rather coarse irradiation defects. The irradiation-induced change of the fracture toughness of single crystal Al2O3 appeared dependent on the crystallographic orientation; both reduced and increased fracture toughness after irradiation was observed. Recent results of neutron irradiation to about 2 × 1025 n/m2 at 100°C showed, that the strength decrease of various Al2O3 grades sets in at (3–5) × 1024 n/m2 and seems to be little dependent on the irradiation temperature. |
