Microstructure anisotropy of nanocrystalline titanium produced by cryomechanical grain fragmentation
Yu.M. Pohribnaya, V.A. Moskalenko, and I.S. Braude
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Nauky Ave., Kharkiv 61103, Ukraine
Received December 19, 2018
Using the x-ray analysis, a systematic study of the deformation microstructure parameters in commercial purity titanium VТ1-0 was carried out. This microstructure is formed as a result of cryorolling at a temperature of 77 K at different degrees of reduction. For determining the existence of the microstructure anisotropy, a comparative analysis of the diffraction pat-terns, the size of the crystallites (coherent scattering regions) L, and the microdeformations values 〈ε2〉1/2 in the rolling plane and in a plane perpendicular to the rolling direction is performed. The analysis in comparison with activity of the operating deformation modes was carried out. Anisotropy in the distribution of the integrated intensities of the diffraction peaks for mutually perpendicular planes is detected. The established difference in the size of the crystallites for the rolling plane and the plane perpendicular to the rolling direction indicates the presence of the shape anisotropy of the crystallites. The effect of the morphological anisotropy of crystallites/grains is most notable for the nanocrystalline state. The observed complex variation microdeformations values 〈ε2〉1/2(e) with deformation is well correlated with the relative activity of slip and twinning. These deformation modes affect the level of local internal stresses and the possibility of their relaxation. The reason of the observed anisotropy of microdeformations may be the presence of oriented grain boundaries associated with the shape anisotropy of the crystallites/grains.
PACS: 61.46.–w Structure of nanoscale materials; PACS: 81.07.–b Nanoscale materials and structures: fabrication and characterization; PACS: 81.40.–z Treatment of materials and its effects on microstructure, nanostructure, and properties.