Selected Area Electron Diffraction, a technique for determination of crystallographic texture in nanocrystalline powder particle of Alloy 617 ODS and comparison with Precession Electron Diffraction

Abstract

Texture analysis in nanocrystalline materials is a challenge. A simple technique as Selected Area Electron Diffraction (SAED) has been used to evaluate texture in a single nanocrystalline Alloy 617 ODS powder particle by carrying out Rietveld texture refinement using Material Analysis Using Diffraction (MAUD) software package and the results were compared with the ASTAR™/Precision Electron Diffraction (ASTAR™/PED) results. Extraction of texture from the SAED patterns involved image analysis and Rietveld refinement of radial plots divided into judiciously chosen angular spans. Inverse pole figure (IPF) from SAED pattern using MAUD revealed 〈110〉 texture parallel to the normal direction (electron beam direction) for unmilled and 6 h milled powders. IPF from ASTAR™/PED technique also shown 〈110〉 lying parallel to the normal direction (beam direction) in both unmilled and the 6 h milled powder. A one is to one correspondence of IPF obtained from MAUD to that of ASTAR™/PED was observed. Texture in unmilled powder could be attributed to the compressive force during rapid solidification in water atomisation process. During the milling process, inhomogeneous rolling and compression of the trapped powder particle in between the balls and between the balls and walls of the jar resulted in shear texture in 6 h milled powder. ASTAR™/PED technique also showed the presence of 〈100〉 //ND texture which was attributed to solidification in unmilled powder and 〈112〉 //ND type texture in milled powder attributed to twin mode of deformation during milling.