Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Surface modification of titanium is of interest considering the necessary improvement of mechanical properties of this material for applications as e.g. medical implants. This work is devoted to the formation of a layer with a high content of the titanium aluminides Ti₃Al and TiAl below the surface by high dose aluminium implantation. If the maximum aluminium concentration exceeds 20 at.% precipitation of Ti 3Al is detected by XRD already in the as-implanted state. For maximum aluminium concentrations between 50 and 55 at.% the phase TiAl is found beside Ti₃Al after annealing at 700^oC. For a double implantation resulting in an aluminium concentration of about 60 at.% in the depth range between 100 and 200 nm a disordered fcc TiAl phase is observed after implantation as precursor for the ordered tetragonal TiAl formed by subsequent annealing at 600^oC. The influence of a pre-implantation of 3x10¹⁷ V/cm² on the phase formation is also reported.
The depth dependent maximum hardness in the near surface range increases with increasing Al dose up to a factor 4. Significantly enhanced wear resistance is observed for Al doses >10¹⁸ cm^-2 after annealing. High dose implantation of Al into Ti results in an enhanced corrosion in 5 M HCl. However, subsequent annealing reduces the corrosion current compared to unimplanted Ti.