Many polycrystalline nickel-based superalloys show localised deformation and stress serrations (Portevin-Le Châtelier Effect) when deformed across an intermediate range of temperatures (300 – 700 °C) and strain rates. Despite its potential technological significance, there does not exist a theoretical or experimental picture to date capable of explaining the atomic scale origins of this behaviour, nor of fully linking between dislocation scale mechanisms and macroscopic features of the serrated flow.

The following work outlines a correlative approach to investigate strain localisation and deformation characteristics across multiple length scales, using the case study of the Portevin-Le Chatelier effect in nickel-based superalloy RR1000, though the methods may be applicable to other applications and alloy systems, for instance investigating strain localisation during crack growth. Multiscale strain mapping, through optical Digital Image Correlation (DIC) and nano-DIC based on Scanning Electron Microscope images, is combined with lattice misorientations from Electron Backscattered Diffraction and dislocation imaging through Electron Channelling Contrast Imaging (ECCI) and Transmission Electron Microscopy, in order to describe the deformation characteristics associated with individual serration events. It is shown that abrupt stress drops are associated with the appearance of broad Lüders bands at random positions within the gauge length. On a finer scale the deformation within those bands is comprised of discrete narrow slip bands across numerous grains.