The Behaviour of Ion Implanted Nitrogen in Niobium: AN Internal Friction Study.

Available from UMI in association with The British Library. The behaviour of ion implanted Nitrogen in metallic materials, particularly BCC Iron, has largely been investigated by examination of the resulting alteration in the surface mechanical properties. This has led to a poor understanding of the behaviour of the implanted Nitrogen and to the development of conflicting theories in an attempt to explain the observations. The interaction of implanted Nitrogen with lattice defects and its behaviour in solid solution was investigated in Niobium as a model system using the internal friction technqiue. Peaks were observed at 220-250K, 429K and 560K as a result of defects produced by implantation. From the behaviour of these peaks it can be deduced that a damage structure consisting of interstitial clusters and short dislocation segments, < 1 times 10^{-7} m, predominates after implantation. Impurity Oxygen introduced from the surface during implantation becomes trapped in the damage structure: this is replaced by Nitrogen on annealing. Nitrogen is retained in solution up to a critical dose of 1 times 10^{17} Ncm^{-2} after which it rapidly becomes trapped as the dose is increased. A general model has been developed to describe the behaviour of Nitrogen during and after implantation. This has been used to reproduce the trend shown by the experimental results.