A critical analysis of the X-ray diffraction intensities in concentrated multicomponent alloys

R Naorem and A Gupta and S Mantri and G Sethi and KV ManiKrishna and R Pala and K Balani and A Subramaniam, INTERNATIONAL JOURNAL OF MATERIALS RESEARCH, 110, 393-405 (2019).

DOI: 10.3139/146.111762

The decrease in the X-ray diffraction Bragg peak intensity from concentrated multicomponent alloys (CMA), has been modeled in literature akin to the effect of temperature. In the current work, experiments and computations are used to comprehend the effect of atomic disorder in CMA on the Bragg peaks of powder diffraction patterns. Ni-Co-Fe-Cr-Mn and Cu-Ni-Co-Fe-V have been used as model systems for the study. It is proved that the intensity decrease is not insignificant, but is not anomalous either. A recipe is evolved to compare the Bragg peak intensities across the alloys of a CMA. It is demonstrated that it is incorrect to model the effect of an increase in atomic disorder in a CMA, as a temperature effect. A 'good measure' of lattice distortion is identified and further it is established that full width half maximum is a good measure of the bond length distortion. It is demonstrated that the true strain due to bond length distortion is of significantly lower magnitude than that given by a priori measures of lattice strain. In the scheme of categorization of defects in crystals, it is argued that CMA is a separate class (as distinct from type-I and type-II defects); which should be construed as a defected solid, rather than a defect in a solid.

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