DEFORMATION HISTORY EFFECTS ON THE PRECIPITATION HARDENING BEHAVIOR OF TI-4+-DOPED SAPPHIRE

The precipitation hardening behaviour of Ti4+-doped (0·08 and 0·17 wt. % Ti02) a-axis sapphire, before and after substantial deformation via the prismatic slip system, has been studied as a function of ageing time in air at 1300°C. Dislocations induced by plastic deformation apparently acted as nucleation sites, as was evidenced by much greater precipitate densities in deformed samples at short ageing times. At ageing times of 13 days or more, precipitate densities were similar for both undeformed and deformed samples. Room-temperature Knoop micro hardness revealed hardness maxima in the [2110] and [1010] directions at ageing times of 16–24 hours and 240–300 hours for both undeformed and deformed samples. Deformed samples aged for 16 hours showed the most significant hardening. Doping level had little effect on the precipitation process and subsequent hardnesses. © 1979 Taylor & Francis Group, LLC.