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.

The paper investigates the dependence of the transformation texture of Zr-2.5wt%Nb tubes and rods on the initial texture, the method of heating (furnacing, conductive heating, inductive heating) and cooling (furnace cooling, water quenching, water shower), stress, and thermal cycling. It was demonstrated that the primary factors determining the transformation texture are the initial texture and the heating rate for quenching. From the investigation results, a method of final thermal treatment of finished zirconium reactor core components (pressure tubes, guide tubes, and cladding fuel rods) is suggested, allowing the destruction of their texture without changing the well-established manufacturing process. The suggested SHF heating includes the use of the α→β→α transformation with fast heating up to the β-phase, subsequent quenching for texture destruction, and annealing for transformation from the metastable α'-state to the equilibrium double-phase αZr + βNb state.

The results of studying the dependence of mechanical properties, corrosion and radiation resistances of hafnium rods on their structure are presented and reviewed in this paper. As observed, the rods in a fully recrystallized state with a finegrained structure possess optimal mechanical properties (high strength and ductility). Tensile strength of these rods at room temperature is of ≈575 MPa, percentage elongation is of 27-28%. Autoclave corrosion tests and anode polarization curves reveal that oxide films formed on hafnium samples in a fully recrystallized state are the most protective that is due to the low surface activity at the medium-metal interface. The corrosion rate of such hafnium rods at the initial period of oxidation (before the pre-transition period) is well described by the empirical power equation with the power coefficient of 0.242 ± 0.015. After the transition point (≈6000 h), the corrosion kinetics is described by a linear dependence with the oxidation rate of 3.12 ⋅ 10 −4 ± 2.07 ⋅ 10 −5 mg/(dm 2 ⋅ h). As shown, there is a correlation between the radiation growth of hafnium rods and their texture coefficient (Kearns's parameter) accor ding to the results of radiation tests carried out at the JSC 'SSC RIAR' (RF) as well as structural-textural studies of the same samples of hafnium rods in various structural states performed in this work. The results presented in this paper reveal that the coefficient of radiation growth linearly decreases with an increase of the Kearns's parameter to a value of 0.33. This indicates that hafnium rod samples with a more isotropic texture are less susceptible to radiation growth. The radiation growths differ, depending on the rods' structure. For rods with the same texture and different grain sizes, the samples with a fine-grained structure are less disposed to radiation growth. While Kearns's parameters are similar, the hafnium rods with a coarse-grained structure show a higher rate of radiation growth. The deformation *

The paper researches into the effect of the initial structural condition of Zr-2.5%Nb alloy, which is widely used in reactor engineering to manufacture reactor core components (mainly as a structural material for RBMK and CANDU pressure tubes), and of irradiation conditions (temperature, applied stress) on irradiation hardening and embrittlement. The reactor damage of Zr-2.5%Nb alloy was modeled with a method of high-energy 225 MeV (e,γ)-beam irradiation, which allows samples to be irradiated under strictly controlled stress conditions. The research has been carried out on Zr-2.5%Nb alloy exposed to four types of thermo-mechanical treatment. It has been found that the alloy is susceptible to intensive irradiation embrittlement irrespective of its initial condition, and the intensity of Zr-2.5%Nb irradiation hardening greatly depends on pre-treatment. In contrast to other conditions, Zr-2.5%Nb alloy is virtually not susceptible to irradiation hardening after high-speed high-frequency (SHF) heating, quenching, and subsequent annealing in the high-temperature range of the α-region, during which the double-phase α+βNb state with high dispersion of βNb (∼1023 m−3) precipitates develops. The obtained results are in good agreement with the post-reactor irradiation tensile test results. The study demonstrates the efficiency of high-energy (e,γ)-beam irradiation for investigating the irradiation hardening and embrittlement of zirconium alloys.