Long-term natural ageing of a dissociated dislocation in a Cu-13.43 at.% Al alloy

The nature of impurity-dislocation interactions is one of the key questions governing the strength and plasticity of solid-solution materials. To investigate the influence of impurities on the mechanical properties of intermetallic NiAl, the electronic structure and energy of NiAl with a <100>{010} edge dislocation and transition-metal impurities was calculated using the real-space tight-binding linear muffin-tin orbital method. The localized electronic states, appearing in the core of the dislocation, are found to lead to strong impurity-dislocation interactions via two mechanisms: firstly, chemical locking, due to strong hybridization between impurity electronic states and dislocation localized states; secondly, electrostatic locking, due to long-range charge oscillations caused by the electron localization in the dislocation core. The results obtained explain qualitatively why the solid-solution hardening effect in NiAl correlates with the electronic structure of impurities rather than with size misfit, as expected according to traditional views.     

Where is here? When is now?1

With a Kleinian perspective influenced by Betty Joseph, the author describes the distinctive ‘here and now’ of a psychoanalysis as the place and the time of the patient’s inner subjective world as it emerges in the work of patient and analyst. This psychoanalytic ‘here’ and ‘now’ is examined with clinical material from the analysis of Mr X; first, with an account of the way his analysis begins and then through a detailed session five years later.The author identifies Mr X’s problems with place and time, and how these change over the course of the analysis. He moves from sequestered dyadic relationships towards an Oedipal and family space, and from disconnection and timelessness to acquiring a sense of duration, of being in the present with a past and a future – all of which, the paper aims to show, has implications for technique.