The microstructure of ball milled nanocrystalline vanadium; variation of the crystal imperfection and the lattice parameter

Abstract Nanocrystalline vanadium powders have been produced by ball milling in a planetary mill. The morphology of the powder particles has been investigated by scanning electron microscopy. Crystallite size (size of coherently diffracting domains) and lattice-strain variation (microstrain) have been determined from the analysis of the X-ray diffraction-line broadening using the established integral breadth Williamson – Hall and Fourier Warren – Averbach methods. Results obtained from transmission electron microscopy analysis have been compared with the X-ray diffraction results. Ball milling causes an increase in the particle size and a decrease in the grain (crystallite) size with increasing milling time, a lattice-strain variation, due to deformation-induced dislocations, that increases with milling time and deformation-induced stacking faults of density increasing with milling time. The lattice parameter of the vanadium powders, as deduced from the diffraction-peak positions, decreases upon milling linearly with the inverse of the grain size, which has been attributed to grain (crystallite)-boundary stress.