Different grain interaction models used for interpretation of lattice strain data collected using grazing incidence X-ray diffraction M. Marciszko 1,3 , A. Baczmański 1 , M. Wróbel 2 , W. Seiler 2 , C. Braham 2 , K. Wierzbanowski 1 1 AGH-University of Science and Technology, WFIS al. Mickiewicza 30, 30-059 Kraków, Poland 2 AGH-University of Science and Technology, WIMIP al. Mickiewicza 30, 30-059 Kraków, Poland 3 Ecole Nationale Supérieure d’Arts et Métiers, PIMM, 151, Bd de l’Hôpital 75013, Paris, France Marianna.Marciszko@fis.agh.edu.pl, Andrzej.Baczmanski@fis.agh.edu.pl, mwrobel@agh.edu.pl, wilfrid.seiler@ensam.eu, chedly.braham@paris.ensam.fr, wierzbanowski@ftj.agh.edu.pl Keywords: X-ray diffraction, grazing incident geometry, X-ray stress factors Abstract. Multireflection grazing incidence X-ray diffraction (MGIXD) was applied to measure residual stresses in thin surface layers. The influence of X-ray stress factors on the interpretation of MGIDX results for polycrystalline materials having respectively low (Ti) and high elastic anisotropy of crystallites (Ni alloy) was considered. It was found that the free-surface model gives the best agreement between experimental and theoretical lattice strains measured in samples having low and high elastic crystal anisotropy. Introduction In this work the problem of X-ray stress factors (XSFs) used for the interpretation of multi- reflection grazing incidence X-ray diffraction (MGIDX),applied for measurement of residual stresses in thin surface layers, is considered. Using the MGIDX method, it is possible to perform a non-destructive analysis of the heterogeneous stress for different and well defined volumes below the surface of the sample, at very shallow depths of a few micrometres (as shown in [1,2]). The MGIDX method was successfully verified by using synchrotron radiation for Al alloy having almost isotropic elastic properties [3].In the present paper, for the first time, four models of grain interactions were used to determine stresses in mechanically treated surfaces using MGIDX method. The aim is to select the most appropriate model, for which the best agreement between theoretical and experimental lattice strains is obtained. MGIXD method is characterized by a small and constant incidence angle for which the penetration depth of X-ray radiation is well defined and does not change during experiment. Measurements are performed for different sets of {hkl} planes using appropriate values of 2θ {hkl} scattering angles. The incidence angle α is fixed during measurement, while the orientation of the scattering vector is characterized by the angle ψ {hkl} =θ {hkl} - α (where ψ {hkl} is the angle between the scattering vector and the surface normal). In the case of the multireflection method applied for cubic crystal symmetry the lattice parameters 2 2 2 { } { } hkl hkl <a( , ) h k l <d( , ) > > ϕψ ϕψ = + + determined from measured interplanar spacings > ) , d( < hkl } { ψ φ are expressed by the macrostresses ij σ and the strain free lattice constant 0 a [1,2]: 0 0 } { a a ] ) , (hkl, F [ = > ) , a( < ij ij hkl + σ ψ φ ψ φ (1) where F ij (hkl,φ,ψ) are the X-ray stress factors (XSFs) [4,5] and φ is the rotation angle around the surface normal. Materials Science Forum Vols. 768-769 (2014) pp 26-30 © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/MSF.768-769.26 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 121.45.186.30, AGH University of Science and Technology, Kraków, Poland-11/09/13,04:26:02)