Fragmentation in Large Strain Cold Rolled Aluminium as Observed by Synchrotron X-Ray Bragg Peak Profile Analysis (SXPA), Electron Back Scatter Patterning (EBSP) and Transmission Electron Microscopy (TEM)

Abstract

In the last decade investigations of plastic deformation have focussed on the large strain ranges, i.e. stage IV and V of deformation [1–5]. Although several models have been developed to explain the work hardening behavior in these stages [2, 6–8], the existing experimental findings are not sufficient to identify the real microstructural processes governing stage IV and V hardening. This situation arises mainly from two facts: (i) traditional methods were not convenient to measure dislocation densities, local internal stresses and misorientation of the substructure, and (ii) most of microstructural investigations were done without relation to the specific mechanical properties. Two new methods, X-ray Bragg Profile Analysis (XPA) [9–12] using a rotating anode and/or synchrotron radiation, and Electron Back Scatter Patterning (EBSP) [13, 14], are effectively for studying microstructures induced by large strains. The XPA-method implemented with a rotating anode generator allows investigation of microstructural evolution within one or more grains by using a focal spot size of several tenth of a mm [15]. Using synchrotron radiation with intensities up to 10¹² photons/mm/s allows a reduction in the footprint of the beam on the sample to an order of a few tens of microns. This allows the investigation of the microstructural evolution within a single grain [16, 17]. The EBSP method evaluates the Kikuchi-line pattern from back scattered electrons in a Scanning Electron Microscope (SEM) with a spatial resolution down to 0. 5 μm. This is done by computer support in a very efficient way so that a very large number of different lattice sites can be studied in short time.