alpha -> omega-phase transformation in titanium induced by power ion-beam irradiation

Irradiation of pure titanium by power ion beams (PIBs) with a power density of 29 MW cm(-2) and a purse of 70 ns was performed. The first pulses of th e PIE lead to the formation of an underlayer with a nanosize structure and of internal compressive macrostresses. Simultaneously a fibre texture with the [11 (2) over bar0](alpha) axis parallel to the ion beam direction is fo rmed. After 30 pulses of the PIE the high-pressure omega phase was detected in titanium. A new orientation relationship between the initial alpha and the final omega phases was found to be (11 (2) over bar0)(alpha)//(12 (3) o ver bar0)(omega) and [10 (1) over bar2](alpha)//[0001](omega). This relatio nship proves a direct phase transformation alpha-->omega. On the basis of t his relationship an atomic mechanism of this transformation is proposed tha t permits us to explain consistently the present and previously reported ex perimental results.