Application of Laboratory Based Laue Micro-XRD for Generalised Grain Orientation Mapping

Abstract

A fully automated laboratory Micro X-ray Laue diffraction system capable of illuminating individual grains in polycrystalline sample is described. A high brightness tungsten micro-focus X-ray source coupled with a capillary focussing optic is used to define a variable spot, ranging in size from 20micron to 200 micron, on the sample. Extension of the Laue technique for micro-texture mapping is then achieved by raster scanning the sample in the focal plane of the focussing optic. The attributes of this new methodology is highlighted by a series of 3 case studies. The first case study demonstrates the high-angular resolution capabilities based on orientation mapping in large grain Si steel electrical transformer plates. An angular resolution better than 0.01degree was readily achieved. Further, the orientation and grain morphology was verified based on synchrotron Laue maps acquired from the same region of interest. Case study 2 addresses the minimum grain size/resolution that can be practically measured. By use of the 20micron probe size orientation maps were acquired for an additive manufactured Ti-5553 wall. A bimodal grain size could be identified. These results were in good agreement with EBSD measurements performed on a sample prepared under the same conditions. Finally, demonstration of large scale grain orientation mapping was performed on an as-received Ti-5553 billet. An orientation map of 65 x 35mm at a step resolution of 0.2mm was used to map the orientation and change in grain morphology across the billet.