α→ ω-phase transformation in titanium induced by power ion-beam irradiation

Irradiation of pure titanium by power ion beams (PlBs) with a power density of 29 MW cm -2 and a pulse of 70 ns was performed. The first pulses of the PIB lead to the formation of an underlayer with a nanosize structure and of internal compressive macrostresses. Simultaneously a fibre texture with the [1120] α axis parallel to the ion beam direction is formed. After 30 pulses of the PIB the highpressure ω phase was detected in titanium. A new orientation relationship between the initial α and the final ω phases was found to be (1120) α //(1230) ω and [1012] α //[0001] ω . This relationship proves a direct phase transformation α → ω. On the basis of this relationship an atomic mechanism of this transformation is proposed that permits us to explain consistently the present and previously reported experimental results.