As shown in Fig. 1, aging the solution-treated Ti-23-11 alloy in the 575'-625'C range results in a significant increase in hardness from -270 VHN to -440-470 VHN. The age hardening occurs rapidly with most of the hardness incr'ease occurring after 3 hours at temperature. In contrast, overaging after peak hardness is attained occurs rather slowly, especially at 5750 C, which suggests rapid nucleation and growth of the hardening phase but sluggish particle coarsening kinetics. While the age-hardening response over a wide range of temperatures has not yet been determined currently for the Ti-23-1 1 alloy, results of tests conducted on material aged 6 hours at temperatures from 3750 to 6750C indicate that peak hardness occurs at 575'C. As such, this is about 100'C higher than is typical of conventional beta Ti alloys (1).