X-ray diffraction characterization of heavily deformed metallic specimens

Ordered intermetallic compound powders can be heavily deformed and disordered by ball-milling. This highly energetic deformation process introduces several kinds of defects into the powder and changes the aspect of the grains. By a novel analysis of the diffraction spectra we can analyse most of such defects and characterize the correlation between the shape of the powder and its crystallographic orientation. In this way we can also recognize how deformation may occur along specific crystallographic planes. The quantitative evaluation of dislocations, twins, stacking and deformation faultings allows us to correlate the disordering process to the introduction and development of defects under the effect of milling. It is shown how a full pattern fitting of diffraction spectra can be successfully applied to a comprehensive investigation of a material modification process, if appropriate physical models are used to describe the scattering event instead of semiempirical functions. (C) 1997 Acta Metallurgica Inc.