Microstructure characterization of nanocrystalline (Ti0.9W0.1) C prepared by mechanical alloying

The microstructural characteristics of nanocrystalline (Ti0.9W0.1)C during mechanical alloying were investigated by using X-ray diffraction. The diffraction crystallite size (DCS) and the microstrain of (Ti0.9W0.1) C ball milled powders have been determined according to various models. The Scherrer and the Stokes-Wilson relations, the Williamson-Hall plot and the Rietveld refinement methods have been employed. The Rietveld method seems to be the best since it gives homogeneous results. The results obtained showed that the (Ti0.9W0.1)C diffraction crystallite size decreases tremendously and its microstrain increases as the milling duration increases. With the further milling of the nanocrystalline (Ti0.9W0.1)C within the stage of the steady-state diffraction crystallite size (8-6 nm), we observed a grain boundary relaxation process that was manifested by evident decreases in the root-mean-square strain, as well as important increases in the dislocation density and the volume fraction. Thus, when the (DCS) is higher than the critical value (8 nm), the plastic deformation is governed by the dislocation sliding mechanism. In the contrary, when the (DCS) is lesser than 8 nm, the plastic deformation is governed by the grain-boundary sliding mechanism. (C) 2015 Elsevier Ltd. All rights reserved.