Formation of the phases Ti₃Al and TiAl by high-dose implantation of aluminium into titanium

Surface modification of titanium is of interest considering the necessary improvement of mechanical properties of this material for
applications as e.g. artificial joints. 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 Ti3Al 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°C. 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°C.