Aging behavior of Ti–Mo alloys heavily compressed in ultra-high strain rate mode

A high density of vacancy clusters was observed in an impact compressed Ti–20Mo specimen to 100% strain. Age-hardening behavior of the specimen at 623 K for 28.8 ks was compared with that of as-quenched specimen. The highest hardness value of both specimens appeared at the aging time of 28.8 ks. The increment of hardness value of the impact compressed specimen due to aging was one-third of that of the as-quenched specimen. At that time, the size of aged ω-particles in the impact compressed specimen were smaller, however, the particle density was higher compared with those in the as-quenched specimen. These results suggest that vacancy clusters introduced by the impact compression become nucleation-sites of aged ω-particles, and a dominant age-hardening mechanism is considered as the pass-through mechanism. Aging behavior of hydrostatically pressurized Ti–15Mo–5Zr specimens at 623 K was investigated, and the maximum hardness value was lower than that of an as-grown Ti–15Mo–5Zr specimen. The results on size and density of aged ω-particles in the hydrostatically pressurized Ti–15Mo–5Zr specimens also suggests that the dominant age-hardening mechanism may be the pass-through one.