Using X-ray structural analysis, features of changes in characteristics of crystallographic texture during cold working of Zr-2.5%Nb alloy plates by longitudinal and cross rolling has been investigated. To make original plates, longitudinal fragments and rings of Æ15.0´1.5 mm² tube annealed at 580 °C were used. The plates were rolled at room temperature to the degrees in the range from 6 to 56% with 5…7% per pass and the rate of 5...10s-1. Using the method of inverse pole figures with measuring by the Bragg-Brentano optical scheme, densities of reflections along normal to plane of the plates (pole densities) was determined. Based on this, distributions of orientations of c-axes of hcp lattice of the material have been analyzed. Local features of the distributions, which were attributed to signs of twinning effects in texture changes in the alloy, are revealed. At subsequent analysis, an effect of strain non-uniformity associated with prehistory of the plates was taken into account. It is established that the second stage of (moderate) changes in Kearns textural coefficient of the plates with the deformation degrees differs from the initial stage of accelerated changes by activation of compression twins. By the method of tilt scanning (of rocking curves) around the Bragg-Brentano position at registration of (0004) reflection intensities, changes in orientation distributions of c-axes in longitudinal and cross section of the plates for both parties were investigated. It is noted that the main textural changes in process of deformation of the plates occur in the cross-sectional plane of the original tube and are most expressed on the cross-rolling plates. The doublet in the distributions of c‑axes, characteristic for rolling texture of hcp metals of titanium subgroup, was noted just at the second stage of the texture changes in the material. Its directionality is mainly associated with the plane of cross-section of the original tube. A connection is revealed between features of the pole density distributions and expression degree of the textural doublet on the rocking curves. According to the results obtained and analysis of other publications, twinning nature of the textural doublet was confirmed and a schematic sequence of its formation was proposed with participation of compression twins of{112-2}{1-1-23} system and tensile twins of {101-2}{1-011} and{112-1}{1-1-26} systems.
-ray studies of the changes in characteristics of crystallographic texture with cold deformation of Zr‑2.5%Nb alloy plates by longitudinal and cross rolling up to 56% at the speed of 5…10 sec-1 were carried out. The original plates were made from longitudinal fragments and rings cut from Æ15.0´1.5 mm² tube, and were then annealed at 580 °C. Texture of the plates was studied by the method of inverse pole figures with calculation of the Kearns texture coefficient along the normal to the plate plane. Dependences of the texture coefficient on degrees of deformation of the plates are built. A discrepancy was found between texture coefficient values measured on different sides of the plates, which is associated with the straightening of the original tube fragments and invariance of “c”-axes distribution after subsequent annealing of the initial plates. By introducing corrections to the degree of deformation calculated from the parameters of the cross section of the original tube, such discrepancies were eliminated for the data on cross-rolling of the material. As a result, for both deformation schemes, two stages of changes in the texture coefficient with alloy deformation were revealed: the initial stage of its growth and the subsequent stage of minor changes. Both stages are mainly linear and have the boundary value of the texture coefficient equal to 0.65...0.68. To study the structural mechanisms of changes in the texture of the alloy, an original technique of comparative analysis of changes in the texture coefficient of the material and in the distribution of crystallographic orientations is applied. It is established that at the initial stage of changes in the texture coefficient with deformation in both schemes, the rotation of the crystallographic “c” axes of the material occurs abruptly, and it does at angles of more than 60°. This confirms the essential role of twinning in the texture changes of the alloy. In particular, we have shown that the initial stage is significantly dominated by the {102}á011ñ system of tensile twins. Connection of twinning with differences in texture changes at the longitudinal and cross rolling of the alloy is discussed.
A scientific and technical development of a high-performance thermal-vacuum method, which is an environmentally friendly process based on combination of vacuuming and high-speed thermal heating, was carried out with non-stop production of nanodispersed carbon. A review of physical processes that affect a powder material has been carried out. Thermal-vacuum treatment of C1 grade graphite 1…2 mm of size was carried out. To study the structural composition of the material in initial state and processed in a thermal-vacuum installation, X-ray diffraction analysis and electron microscopy were used. According to results of X-ray analysis, the original C1 grade graphite has two known structural modifications: hexagonal one with lattice periods a o = 0.2461 nm, c o = 0.6705 nm, and rhombohedral structure about 30% -with a = 0.2461 nm and c = (3/2)c o = 1.003 nm. In graphite treated in a thermal-vacuum installation, these components have been detected as the main composition. Additionally, a super-structural rhombohedral phase with periods a = 2a o = 0.492 nm and c = (3/2)c o = 1.003 nm has been detected. A monoclinic phase with parameters a 1 = 0.6075 nm, b 1 = 0.4477 nm, c 1 = 0.4913 nm, and β = 99.6° has also been detected, probably with the presence of iron atoms in structure. The results of analysis and calculations are generally consistent with TEM images of the reciprocal lattice of processed graphite. As a result, it was noted that the initial graphite powder was crushed to 2…40 nm with a partial change in the structure, formation of objects like multilayer nanotubes and fullerenes. It was noted that thermal deformations are involved in this effect, what can significantly accelerate the process of obtaining nanodispersed carbon material with new physicochemical and mechanical properties. The results could be widely used for industrial production of nanosized materials.
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