Papers by Author: Julie M. Cairney

Abstract: Atom probe tomography provides compositional information in three dimensions at the atomic scale, and is therefore extremely suited to the study of nanocrystalline materials. In this paper we present atom probe results from the investigation of nanocomposite TiSi¬Nx coatings and nanocrystalline Al. We address some of the major challenges associated with the study of nanocrystalline materials, including specimen preparation, visualisation, common artefacts in the data and approaches to quantitative analysis. We also discuss the potential for the technique to relate crystallographic information to the compositional maps.

Abstract: This study investigates the effect of N diffusion on a Nb-microalloyed steel made by twin roll casting at 525o C in a KNO3 salt bath. Nitriding up to 4 h increases the yield strength of the steel by ~50% with only a small drop in ductility, while 6 hours of nitriding causes brittle fracture. The improved mechanical performance after 4 hours of nitriding is thought to be a combined effect of solid solution strengthening of N diffusion and dispersion strengthening from extremely fine Nb-rich precipitates. Coarse features along grain boundaries consistently observed in steel nitrided for 6 hours are considered to be responsible for brittle fracture in samples nitrided for longer.