Lattice location and diffusion of W implanted in Mg and Al single crystals

Tungsten was implanted in Mg single crystals at 293 and 77 K. A rather high substitutional fraction, fs=0.8, was observed after implanting W at 293 K with peak concentrations up to 0.3 at.%. With increasing peak concentration up to 2.7 at.% W, fs decreases to 0.3. Implanting 0.3 at.% W at 77 K resulted a fs value of 1, which did not change after warming up to 293 K. Annealing at 553 K causes a recovery of the host lattice, which however does not affect fs. The diffusion of W in Mg is much lower than expected from the Mg self-diffusion coefficient, which may be explained by internal oxidation of the W atoms. In the case of the WAl system, W is completely substitutional after implantation at 293 and 7 K up to peak concentrations of about 5 at.%. (orig.)