An X-ray diffraction study of nanocrystalline titanium prepared by high-energy vibrational ball milling

Abstract

A detailed X-ray line-broadening study in ball-milled Ti sample is presented. It is observed that ball milling leads to the formation of nanocrystalline grains and transform partially to an f.c.c. Ti-phase after 10 h of milling. Using a Rietveld analysis, the volume fraction of f.c.c. phase was found to be ∼24% with a crystallite size of ∼20 Å. The origin of high strains is probably the dislocations present in the sample. Anisotropic line broadening of the fault-unaffected reflections is explained in terms of anisotropic dislocation contrast corresponding to 〈 a〉 and 〈 a+ c〉 dislocations. Both edge and screw dislocations were predicted with a significant basal slip. High dislocation density ∼10 11 cm/cm 3 has been found in the milled samples. A large increase in the isotropic thermal parameter was also observed for the h.c.p. Ti-phase after 10 h of milling.