Influence of gamma radiation on the microhardness of high-alumina ceramics

Microhardness (Hμ) of commercial ceramics samples manufactured on the α-Ai2O3 base before and after of irradiation by Co60 isotope gamma-quanta within dose range 105-109 rad is measured. It is shown, that gamma radiation leads to Hμ value increase for all samples. Growth of Hμ value correlates with crystallites size and crystalline phase amount in the ceramics. Sharp growth of Hμ with dose increase it is especially noticeably in material with a great amount of crystalline phase. At the further increase of the gamma dose up to 106 rad the Hμ value is achieves the maximal value, and then at the 107 rad dose it is reducing and becomes even less than the initial value, and at following radiation dose the Hμ value is monotonously increasing. Such anomalous behavior of Hμ value is noticed for all examined samples. It is suggested, that radiation conducts to surface layer improvement for examined samples. One of the possible mechanisms responsible for this effect may serves electronically induced processes (discharge and defects re-distribution under radiation effect)