Diffraction Stress Analysis of Strongly Fibre-Textured Au Layers

Atul Kumar, Udo Welzel and Eric J. Mittemeijer

Max Planck Institute for Metals Research, Heisenbergstr. 3, D-70569 Stuttgart, Germany

Diffraction stress analysis on the basis of the so-called sin²y-method is a well-established method. However, a straightforward application of the sin²y-method, using the so-called X-ray elastic constants (XECs) and , is possible only if the specimen is macroscopically elastically isotropic. This implies that the sin²y-method (based on XECs) can not be applied to crystallographically textured specimens, because for such specimens, macroscopic, mechanical anisotropy generally occurs.

For specimens presenting crystallographic texture that is both strong (i.e. the random texture fraction is small) and sharp (i.e. the orientations of crystallites exhibit only small spreads from the ideal orientations), the so-called crystallite group method has been proposed [1,2]. As proposed the method was intended for single-crystal like textures only. The crystallite group method can also be adapted to deal with specimens presenting a fibre-texture [3].

In this work, the crystallite group method has been employed for the diffraction stress analysis of fibre-textured gold films. The consequences of the macroscopically elastically anisotropic nature have been demonstrated. Further, possible alternative measurement strategies, i.e. the use of one reflection versus the use of multiple reflections, and the corresponding procedures required for calculating lattice strains from measured lattice spacings, have been discussed in particular in view of the susceptibility of the obtained stress results to instrumental aberrations. The ranges of applicability of the crystallite group method in view of texture strength, sharpness and complexity and with respect to possible mechanical loading states (biaxial rotationally symmetric versus biaxial) have also been analysed.

[1] Willemse P. F., Naughton, B. P. & Verbraak C. A., 1982, Mater. Sci. and Eng. 56, 25.

[2] Willemse P. F. & Naughton, B. P., 1985, Mater. Sci. Techn. 1, 41.

[3] Baron, H. U. & Hauk, V., 1988, Z. Metallkde. 79, 127.