Hardening in MgO·3.0Al2O3 by neutron irradiation

MgO·3.0Al2O3 single crystalline samples were irradiated with fast neutrons in various conditions and the hardness of the irradiated and unirradiated samples was measured with a Vickers hardness tester. The hardness of an as-irradiated sample increased by 23 %. After isochronal annealing, the hardness gradually decreased and mostly recovered to that of the unirradiated one above 600 °C, and fully recovered after annealing at 900 °C. Volume of the sample also increased after the irradiation and changed in the same way as the hardness by annealing. A relation between hardness and density of point defects is proposed and the experimental results agree with the relation. It implies that the point defects pin down dislocations generated by the indentation and increase the hardness of neutron irradiated MgO·3.0Al2O3 samples.