Measurements of Debye-Waller factors in TiAl from energy-filtered HOLZ line intensities

Abstract

This paper reports a new method to measure Debye Waller factors. The measurements are required for subsequent structure factor refinement in TiAl. The procedure is to obtain a large angle CBED pattern near a sparse zone axis, extract line scans along HOLZ lines from this pattern and use two beam intensity calculations to fit experiment and simulation by varying the Debye Waller factors. Unlike earlier work, we have used non-systematic reflections. The material studied is γ−TiAl (50-50), made from 25g ingots produced by arc-melting in an argon atmosphere, and homogenized for 1 day at 1473 K. Specimens were thinned by twin-jet electropolishing.Elastic energy filtered patterns are required for accurate quantitative comparisons between experiment and theory. A Zeiss 912 Omega TEM/STEM electron microscope was used to obtain energy filtered CBED patterns, fitted with an Omega imaging energy filter, which forms images or diffraction patterns within any desired energy loss range.