Features of processes of recrystallization in rolled single crystals and polycrystals of zirconium and alloy Zr-1% Nb have been analyzed. To estimate the crystallographic texture and structural state

Integral texture Kearns parameters, or f-parameters, are the one of the characteristics that is controlled during the tube production of Zr-based alloys now. These parameters define the anisotropy of physical and mechanical properties of the products. f-parameters are the sum of effective fractions of basal normals aligned in a selected sample direction. However, so far there is no standardized procedure for their calculation. The widespread availability of X-ray diffractometers, the high statistical significance of the results and the software development for texture analysis causes the optimality of the f-parameters determination by complete pole figures (0001) calculated through orientation distribution function (ODF). Accuracy analysis of the ODF extraction by several incomplete pole figures using LaboTex software was carried out in this paper. The comparison of the calculated data was performed with experimental complete pole figures (0001) obtained by «sewing» method. Various texture types, different number and combinations of incomplete pole figures were considered. For this purpose, 6 incomplete pole figures - - were registered for each of three mutually perpendicular surfaces of the CANDU-tube sample. By comparison of experimental and calculated by ODF complete pole figures as well as f-parameters, procedures of their determination were optimized for products from Zr-based alloys.

The method for grain size determination by statistical fluctuations of X-ray intensity, registered during measurement of texture pole figures, was developed. Niobium and bronze rods as well as tubes from Zr-1%Nb alloy, subjected to annealing at different temperatures, were studied. Description of the method, pole figures (PF), X-ray intensity distribution within PF circular sections, grain size values and their errors are presented.

Based on the data of synchrotron and electron microscopic studies of deformed and annealed Russian zirconium alloys, the possibility of analyzing the structural-phase state and crystallographic texture of individual phases has been demonstrated. A qualitative and quantitative phase analysis of deformed and annealed tubes made of Zr-Nb-(Sn-Fe-O) alloys was carried out using diffraction patterns obtained with synchrotron radiation. The main α-Zr phase and the following additional phases: β-Nb, β-Zr, and the Laves phase (intermetallic compound Zr(Nb,${\mathrm{Fe})}_2$), were found in the alloys. According to the results of texture analysis of all phases present in the alloy, the mechanisms of plastic deformation, recrystallization, and phase transformations of the main and additional phases were established. It is shown that during plastic deformation of the Zr-1%Nb alloy, a dynamic phase transformation β-Nb→α-Zr→β-Zr is observed. It is established that during recrystallization, larger grains of α-Zr are misoriented relative to the deformed matrix by rotating the prismatic axes around the basal axes by 30°, while fine grains are improved by polygonization and maintain the orientation of the deformed matrix. Processes for changing the orientation of grains of additional phases as a result of high-temperature annealing are also considered.

Electron microscopic studies of the surface of the spacecraft descent vehicle (DV) have revealed faceted particles of various shape and size, which are formed when the DV travels through the Earth’s atmosphere at an ultrasonic velocity. The particles are no more than 5 µm in size. An X-ray diffraction analysis of the phase composition of the precipitate on the DVs porthole after their landing showed that the test samples contain the following minerals: сryptohalite—(NH₄)₂[SiF₆]), sal ammoniac—NH₄Cl, mullite—Al₂SiO_5, and other minerals that rarely occur in nature. The paper presents results of electron microscopic and X-ray studies of samples taken from 4 descent vehicles.

The indentation size effect on the hardness of polycrystalline niobium has been studied. A relationship between the material hardness and the indenter mark dimensions is established in a broad range of indentation depths (20 nm–70 μm).