Phase formation tuning of oxygen-implanted layer on Ti6Al4V and Ti by annealing

Ti6Al4V and Ti were implanted by oxygen plasma based ion implantation at the pulsed negative voltages of 30 and 50kV with a constant fluency of 4×10¹⁷ O/cm². In order to tune phase formation in the oxygen-implanted layer, the implanted samples were treated by subsequent annealing in atmosphere or vacuum for 1h at the temperatures from 500 to 700°C, respectively. The annealing mediums such as vacuum or atmosphere have a strong influence on the structure in the implanted layer. The annealing in atmosphere could promote phase formation and transformation. The higher voltage (50kV) implantation forms directly nano-size rutile in the implanted layer. And the subsequent annealing induces the growth of rutile, but does not lead to anatase phase with increasing temperature. The lower voltage (30kV) implantation does not lead to rutile, but the annealing can precipitate mixture phases of anatase and rutile in the oxygen-implanted layer at 650 and 550°C for Ti6Al4V and Ti, respectively. Post implantation annealing contributes a larger increase in surface roughness with increasing temperature.