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Hydrogen diffuses in zirconium alloys in response to gradients in hydrogen concentration, temperature, and stress. This essay discusses the results of several evaluations of the coefficient describing the effects of temperature gradients called the heat of transport. The values distinguish between when hydrogen is in solution, (25 ± 3) kJ/mol, and when stable hydrides are present, (116 ± 17) kJ/mol. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Zirconium alloy with the composition of 90.1% Zr and alloying elements such as Mg, Al, and Si was investigated for its mechanical properties and corrosion resistance. The specimen was dissolved in a mixture of NaOH, Na2CO3, S, and SnO2 at 800°C for 10 min, followed by an HCl solution at room temperature for 100 cycles. The structural properties were characterized by X-ray diffraction and scanning electron microscopy, while the mechanical properties, such as tensile strength were investigated by a universal tensile machine. The microstructural observations indicated that the outside part of the crucible underwent pitting corrosion which resulted in corrosion in all directions inside that part of the crucible. The corrosion structure consisted of cracks that reached the base metal. The residual chemical from the fusion and dissolution process remained in the crack and formed NaCl, which accelerated the crack. The release rate of the zirconia oxide layer was calculated to be 8 μm per cycle. During the corrosion process at high temperatures, oxygen diffusion infiltrated the base metal and stretched the crystal lattice, causing strain hardening with the values of yield strength and ultimate tensile strength increased to 22.5% while the strain decreased by 50%. [ABSTRACT FROM AUTHOR]

Delayed hydride cracking (DHC) is a hydrogen embrittlement phenomenon that may potentially occur in Zircaloy-4 fuel claddings during dry storage conditions. An experimental procedure has been developed to measure the toughness of this material in the presence of DHC by allowing crack propagation through the thickness of a fuel cladding. Notched C-ring specimens, charged with 100 wppm of hydrogen, were used and pre-cracked by brittle fracture of a hydrided zone at the notch root at room temperature. The length of the pre-crack was measured on the fracture surface or cross-sections. Additionally, a finite element model was developed to determine the stress intensity factor as a function of the crack length for a given loading. Two types of tests were conducted independently to determine the fracture toughness with and without DHC, K I DHC and K I C , respectively: (i) constant load tests at 150 ∘ C, 200 ∘ C, and 250 ∘ C; (ii) monotonic tests at 25 ∘ C, 200 ∘ C, and 250 ∘ C. The results indicate the following: (1) there is no temperature influence on the DHC toughness of Zircaloy-4 between 150 and 250 ∘ C ( K I DHC ∈ 7.2 ; 9.2 MPa m ), (2) within this temperature range, the fracture toughness of Zircaloy-4 is halved by DHC ( K I C ∈ 16.9 ; 19.7 MPa m ), (3) the crack propagation rate decreases with decreasing temperature and (4) the time before crack propagation increases as the temperature and loading decrease. [ABSTRACT FROM AUTHOR]

In pressurized water reactors, LiOH may be concentrated in some areas, leading to the accelerated corrosion of fuel claddings. Injecting boric acid into primary coolants can mitigate the accelerated corrosion effect of LiOH on Zircaloys, but the effects of boron content on the corrosion behavior of the Zr-Sn-Nb alloy are still unknown. This work focused on the corrosion and hydrogen absorption behavior at 360 °C/18.6 MPa in 100 mg/kg LiOH solutions with 0 mg/kg, 50 mg/kg, and 200 mg/kg boron contents for up to 510 days, aiming to study the effect of boron content on corrosion resistance in LiOH solutions. Corrosion kinetics, microstructures of oxide films, hydrogen absorption concentrations and hydride morphology were obtained after the test. The results show that injecting boron in LiOH solutions can significantly reduce the corrosion weight gain, hydrogen concentration, and hydrogen length of Zr-Sn-Nb alloys, that is, improving corrosion resistance effectively. During the oxidation of the Zr-Sn-Nb alloy, B3+ and Li+ incorporate in oxide films. The incorporation of Li+ may lead to the generation of oxygen vacancies, which can carry oxygen from the solutions to O/M interface, accelerating corrosion. The incorporation of B3+ in oxide films will slow down the oxidation of Zr-Sn-Nb alloys by reducing the oxygen vacancies caused by Li+ aggregation. [ABSTRACT FROM AUTHOR]

The present study demonstrates the development of novel Ti-xZr (x = 5, 10, 15 and 20 wt.%) via vacuum sealing-assisted sintering technique. The microstructure, phase composition, physical, mechanical, tribological properties, and electrochemical corrosion behavior were investigated for biomedical applications. The phase composition and microstructure show the presence of α phases in as-prepared alloys. The alloys exhibit elevated hardness levels (477.59 ± 30.22 HV to 539.05 ± 27.09 HV), surpassing commercially pure titanium (cpTi, 200.26 HV) and Ti-6Al-4V (340.51 HV). Tribological studies of Ti-15Zr displays superior antifriction and antiwear properties, with a friction coefficient of 0.22 and a wear rate of 1.23 × 10–7 mm3 per mm of sliding distance. All alloys exhibit commendable corrosion resistance in simulated body fluid, with the Ti-20Zr alloy displaying a minimum corrosion rate of 1.29 µm/year. In conclusion, the synthesized alloys demonstrate the substantial potential for biomedical applications, particularly in orthopedic and dental implants, due to enhanced mechanical characteristics, wear resistance, and corrosion resistance. [ABSTRACT FROM AUTHOR]

Copyright of Materialwissenschaft und Werkstoffechnik is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Operated under extreme conditions, corrosion occurs between zirconium alloy cladding tubes and the coolant in the primary loop of pressurized water reactors (PWRs), contributing to a reduction in the effective metallic material thickness. Therefore, understanding the corrosion behavior of zirconium alloy is vital to both raising the burnup of PWR and the improvement of safety properties of these reactors. During the past decades, extensive investigation was conducted with various conditions, such as changing corrosion temperatures and alloying elements, but contradiction persists and universal conclusion remain elusive. In the present work, a variety of research results that focused on corrosion kinetics, microstructural evolution, and the influence of alloying elements were integrated and summarized, so that a valuable reference can be provided to further research. [ABSTRACT FROM AUTHOR]

In this work, fuzzy model was developed that predicts response parameters and surface properties of an electrical discharge machined Zircaloy-2. Taguchi L18 mixed design was used to perform the experiments using different process parameters (polarity, pulse-on-time, pulse-off-time, tool electrode material, and peak current). Material removal rate (MRR) and tool wear rate (TWR) were chosen as machining response parameters, whereas number of particles (NoP) and the percentage particle area (PPA) for surface properties of EDMed surface. Digital image processing tool was used to evaluate the surface properties. Fuzzy-Sugeno (FS)-model was developed to predict MRR, TWR, NoP, and PPA. Model accuracy was found to be 94% for MRR and TWR, and 92% for NoP and PPA. Maximum MRR 1.53 × 10−3 mm3/min found when machining was performed using graphite tool with negative polarity. Fuzzy Sugeno-GRA method was successfully implemented to predict optimal response corresponding to high value of GRG. [ABSTRACT FROM AUTHOR]

The microstructure evolution associated with the cold forming sequence of an Fe-14Cr-1W-0.3Ti-0.3Y2O3 grade ferritic stainless steel strengthened by dispersion of nano oxides (ODS) was investigated. The material, initially hot extruded at 1100 °C and then shaped into cladding tube geometry via HPTR cold pilgering, shows a high microstructure stability that affects stress release heat treatment efficiency. Each step of the process was analyzed to better understand the microstructure stability of the material. Despite high levels of stored energy, heat treatments, up to 1350 °C, do not allow for recrystallization of the material. The Vickers hardness shows significant variations along the manufacturing steps. Thanks to a combination of EBSD and X-ray diffraction measurements, this study gives a new insight into the contribution of statistically stored dislocation (SSD) recovery on the hardness evolution during an ODS steel cold forming sequence. SSD density, close to 4.1015 m−2 after cold rolling, drops by only an order of magnitude during heat treatment, while geometrically necessary dislocation (GND) density, close to 1.1015 m−2, remains stable. Hardness decrease during heat treatments appears to be controlled only by the evolution of SSD. [ABSTRACT FROM AUTHOR]

A dense and continuous Cr coating with a thickness of approximately 140 μm was successfully deposited on the surface of a thin-walled Zr alloy cladding tube using high-speed laser cladding technology in this study. The microstructure, phase composition, microhardness, and resistance to high-temperature oxidation of the coating were investigated. The experimental results showed that the Cr coating exhibited high-strength metallurgical bond with the Zr alloy substrate, forming a narrow heat-affected zone with a thickness of 25 μm, and the coating consists of ZrCr2 and α-Zr phase. The average microhardness of the coating was 589 HV0.05, about 2.3 times that of the substrate. After oxidation at 1200 °C for 1200 s in air, with the formation of complete and dense protective Cr2O3 scale, the Cr-coated Zr alloy cladding tube showed better high-temperature oxidation resistance than uncoated tube. [ABSTRACT FROM AUTHOR]

Jetting in cylindrical cumulation is an elusive process. This paper investigates cumulative jetting during the compression of cylindrical shells by means of a hydrodynamic model and numerical simulation. A method for improving jetting in cylindrical cumulation that increases the radial velocity of shell convergence has been proposed and substantiated. The critical factor in the jet-formation zone—high temperature—is outlined. A method of normalizing the temperature in the jet-formation zone using a small diameter tube inside the main cladding made of refractory niobium has been proposed. Thus, suggestions were made to improve cumulative jetting in cylindrical cumulation. [ABSTRACT FROM AUTHOR]

In the present study, the dense Cr and Cr0.92Si0.08 coatings have been deposited on Zircaloy-4 substrates by the magnetron sputtering technique. The high-temperature oxidation resistance of coatings is evaluated in 1200 °C steam for 1–4 h. The Cr0.92Si0.08 coating shows better oxidation resistance than the Cr coating. The in-situ formed Zr2Si diffusion barrier inhibits the mutual diffusion of Cr and Zr. And the formation of a Cr2O3/SiO2 double-layer scale effectively improves the oxidation resistance of a single Cr2O3 layer. The formation of the in-situ diffusion barrier, Cr2O3/SiO2 scales and oxidation protection mechanisms of the Cr0.92Si0.08 coating have been discussed in detail. [ABSTRACT FROM AUTHOR]

Zirconium alloys are critical material components of systems subjected to harsh environments such as high temperatures, irradiation, and corrosion. When exposed to water in high temperature environments, these alloys can thermo-mechanically degrade by forming hydrides that have a crystalline structure that is different from that of zirconium. Cracks can nucleate near these hydrides; hence, these hydrides are a direct link to fracture failure and overall large inelastic strain deformation modes. To fundamentally understand and predict these microstructural failure modes, we interrogated a finite-element database that was deterministically tailored and generated for large strain-dislocation-density crystalline plasticity and fracture modes. A database of 210 simulations was created to randomly sample from a group of microstructural fingerprints that encompass hydride volume fraction, hydride orientation, grain orientation, hydride length, and hydride spacing for a hydride that is physically representative of an aggregate of a hydride population. Machine learning approaches were then used to understand, identify, and characterize the dominant microstructural mechanisms and characteristics. We first used fat-tailed Cauchy distributions to determine the extreme events. A multilayer perceptron was used to learn the mechanistic characteristics of the material response to predefined strain levels and accurately determine the critical fracture stress response and the accumulated shear slips in critical regions. The predictions indicate that hydride volume fraction, a population-level parameter, had a significant effect on localized parameters, such as fracture stress distribution regions, and on the accumulated immobile dislocation densities both within the face centered cubic hydrides and the hexagonal cubic packed h.c.p. matrix. [ABSTRACT FROM AUTHOR]

A Canada Deuterium Uranium (CANDU) reactor has hundreds of carbon steel feeder pipes that are connected at one end to the fuel channels at the reactor face and are connected at the other end to the reactor inlet and outlet headers above the reactor. The production of hydrogen gas from metal–water interaction at high temperatures is a major concern during a severe accident in a nuclear reactor. It is generally accepted that the main source of hydrogen gas during a severe accident is the chemical interaction of Zircaloy fuel cladding and the water coolant. However, it has recently been suggested that the amount of hydrogen produced by the oxidation of carbon steel located outside of a CANDU core could exceed that produced by zirconium oxidation. In this work, the linear and parabolic oxidation rate constants of CANDU feeder carbon steel, in the temperature range of 600–1,100°C, were measured to be W/t = 1.806 × 103 exp (− 126,337/RT) and W2/t = 1.879 × 105 exp (− 135,835/RT), respectively. For parabolic steam oxidation beginning at roughly 90 minutes after reaching steady-state heating temperatures, the latter equation should be used. These rates are about a factor of 5–10 greater than oxidation rates measured in 304L stainless steel and in zirconium specimens, meaning that the carbon steel oxidation can be significant in an accident. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering Sciences is the property of Faculty of Engineering - Assiut University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The hydrogen terminal solubilities for dissolution (TSSD) and precipitation (TSSP) in non-irradiated sponge-based E110opt alloy and electrolytic zirconium E635 alloy are presented. TSS measurements for these alloys were made for the first time. Samples were examined using the methods of differential scanning calorimetry (DSC) and hot vacuum extraction spectrometry. Terminal solid solubilities (TSSD and TSSP) in E110opt and E635 alloys are shown to be coincident with each other within the experimental uncertainty interval. This means that there is no distinguishable difference between TSS in sponge-based and electrolytic zirconium alloys. Resulting TSSD values for E110opt and E635 alloys were compared with those for zirconium alloys Zircaloy-2, Zircaloy-4, Zr-1%Nb, M5, Zirlo and shown to be identical within the errors. Approximation dependencies of TSSD and TSSP solvi in E110opt and E635 alloys were derived. These dependencies will be used in nuclear fuel performance codes to calculate behavior of the zirconium reactor core components in different regimes of operation. [ABSTRACT FROM AUTHOR]

Accident-tolerant fuel concepts have been developed recently in diverse research programs. Recent research has shown clear advantages of Cr-coated Zr cladding over bare cladding tubes regarding oxidation behavior under the design basis loss-of-coolant accident condition. However, limited data are available about the hydriding behavior of the Cr coating. For that purpose, Cr-coated Zricaloy-4 tubes were tested to investigate the effects of hydriding, oxidation, and postquench ductility behavior on coated Zr cladding. A high-power impulse magnetron sputtering (HiPIMS) process was used to produce a high-density coating on the Zircaloy-4 tube surface. Coated and uncoated Zircaloy-4 tube specimens underwent one-sided hydriding in a tube furnace filled with pure hydrogen gas at 425 °C. The tubing specimen ends were sealed with Swagelok plugs before the hydriding runs. For uncoated specimens, H analysis of the hydrided specimens indicated that the H content increased as the test time and initial pressure increased. However, almost no change was observed for the coated specimens that were hydrided under the same test conditions. After one-sided hydriding, the hydrided coated and uncoated specimens were exposed to steam at high temperatures for two-sided oxidation studies to simulate accident conditions. The coated specimens showed a slower oxidation: oxygen pickup was 50% lower than the uncoated specimens tested under the same conditions. Ring compression testing was performed to evaluate the embrittlement behavior of the Cr-coated specimens after hydriding and oxidation. The results indicated that the HiPIMS coating provides excellent protection from hydriding and oxidation at high temperatures. [ABSTRACT FROM AUTHOR]

Zircaloy-2 is used in nuclear and biomedical industries therefore required high accuracy and precision, and achieved by application of electrical discharge machine (EDM). In this study, a new horizon of tool design is investigated for improvement in the performance of EDM. To measure the effect of tool design, Zircaloy-2 is machined with EDM using progressive Cu tool and measured the response parameters (MRR, TWR, radial overcut (Roc), radial undercut (Ruc), taper angle (Φ), and surface roughness). The progressive tool with varying design parameters of rake angle (0°, 45°, and 60°), flat land (2 mm), trunk diameters (10, 8, and 6 mm), and relief angle (0°, 45°, and 60°) are used to perform rough and finish machining in single EDM operation. MRR and SR are increased with increase in rake angle due to reduction in oxide and carbide deposition on the machined surface. Best combination for maximum MRR (1.131 × 10−3 mm3/min), minimum SR (4.313 µm), and minimum taper angle (2.17°) is obtained when machining is performed using T7. Multiresponse optimization (R-method) gives highest rank to progressive tool T7. Tool design improved TWR and significant reduction in radial overcut over conventional tool. [ABSTRACT FROM AUTHOR]

Cr-coated Zr alloys are widely considered the most promising accident-tolerant fuel (ATF) cladding materials for engineering applications in the near term. In this work, Cr coatings were prepared on the surfaces of 1400 mm long N36 cladding tubes using an industrial multiple arc source system. Orthogonal analyses were conducted to demonstrate the significance level of various process parameters influencing the characteristics of coatings (surface roughness, defects, crystal orientation, grain structure, etc.). The results show that the arc current mainly affects the coating deposition rate and the droplet particles on the surface or inside the coatings; however, the crystal preferred orientation and grain structure are more significantly influenced by the gas pressure and negative bias voltage, respectively. Then, the underlying mechanisms are carefully discussed. At last, a set of systemic methods to control the quality and microstructures of Cr coatings are summarized. [ABSTRACT FROM AUTHOR]

In this paper, the cladding of pure aluminum and a low-carbon steel alloy was performed through friction stir processing with minimal intermetallic compound formation. A 3 mm thick aluminum plate was clamped on top of a steel plate. A thick, pure copper plate was used as a backing plate. The tool pin length was adjusted to be the same as the upper plate's thickness (3 mm) and longer than 3.2 mm. The effect of the tool pin length and the rotation speed (500–1500 rpm) on the cladding's quality, microstructure, and the mechanical properties of the steel/aluminum interface were investigated using optical and scanning electron microscopy, a hardness test, and a peel test. The results showed that the bonding of pure aluminum and a low-carbon steel alloy can be successfully performed at a more than 500 rpm rotation speed. At a tool pin length of 3 mm and a rotation speed of 1000 rpm, sound and free-intermetallic compound–cladding interfaces were formed, while some Fel2Al5 intermetallics were formed when the rotation speed was increased to 1500 rpm. The pure copper backing plate has an essential role in eliminating or reducing the formation of intermetallic compounds in the cladding interface. When the tool pin length was increased to 3.2 mm, more steel fragments were found on the aluminum side. Moreover, with a higher rotation speed and longer tool pin length, more Fe2Al5 intermetallics were formed at the interface. Increasing the rotation speed and the pin tool length contributed to the enhancement of interface bonding. Meanwhile, the maximum tensile shear load was obtained at a rotation speed of 1500 rpm and a tool pin length of 3.2 mm. In addition, the hardness values of the interface were higher than the aluminum base metal for all the investigated samples. Decreasing the rotation speed and increasing the tool pin length can significantly increase hardness measurements. The average hardness increases from 42 HV of the pure aluminum to 143 HV at a rotation speed and a tool pin length of 1500 rpm and 3.2, respectively. [ABSTRACT FROM AUTHOR]

In the pressurized water reactor nuclear power plant, 316L SS chips were captured by the support grid and continued to affect the Zr-4 cladding tube, causing the fuel rods to wear and perforate. In this work, a 60° acute angle cone of 316L SS was used to simulate the cyclic impact of debris on a Zr-4 alloy tube with different initial impact velocities and impact angles. Results showed that increasing the initial impact velocity will generate a wear debris accumulation layer with a wear-reducing effect, but also promote the extension and expansion of fatigue cracks, resulting in the delamination of Zr-4 alloy tubes. The inclination of the impact angle increases the energy loss. The energy loss rate of the 45° impact is as high as 69.68%, of which 78% is generated by the impact-sliding stage. The normal force is mainly responsible for the wear removal and plastic deformation of Zr-4 alloy tubes. Tangential forces cause severe cutting in Zr-4 alloys and pushes the resulting wear debris away from the contact surfaces. [ABSTRACT FROM AUTHOR]

In order to maximize the performance of the nickel-based cladding layer without adding a reinforcing phase, ultrasonic vibrations of different frequencies are assisted in the laser cladding process. The morphology of the cladding layer was analyzed by a metallographic microscope, the microstructure of the cladding layer was analyzed by SEM, the element segregation of the cladding layer was analyzed by EDS energy spectrum, and the microhardness of the cladding layer was tested by a microhardness tester. Hardness and friction-wear performance of the cladding layer were tested using a friction and wear tester. The test results show that the appropriate ultrasonic frequency can obviously refine the microstructure of the cladding layer, the hardness and wear resistance of the cladding layer have been significantly improved due to the refinement of the structure, and it has a good fine grain for the cladding layer. The strengthening effect maximizes the performance of the cladding layer. [ABSTRACT FROM AUTHOR]

The preparation of functional coatings on metal substrates is an effective method to enhance the surface of steel structures with good serviceability in applications for engineering parts. The objective of this research is to analyze the surface properties of two sorts of medium-entropy alloy (MEA) coatings prepared by laser cladding. After cladding, the two prepared coatings were strengthened by ultrasonic burnishing (UB) treatment. Cladding coating samples before and after being UB-treated were comparatively tested in order to investigate the process effects of UB. When compared with corresponding untreated coating samples, the roughness values of the two sorts of UB-treated samples were decreased by 88.7% and 87.6%, the porosities were decreased by 63.8% and 73.4%, and the micro-hardness values were increased by 41.7% and 32.7%, respectively. Furthermore, the two sorts of UB-treated coating samples exhibited better mechanical properties and wear resistance than corresponding untreated samples. [ABSTRACT FROM AUTHOR]

The present work aims to study evolutions of the metallurgical structure and the interfacial interactions in the SS-304L/Zy-4 dissimilar junction during isothermal holding at high temperature. The obtained interfaces were characterized by the combination of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), electron probe micro-analyzer techniques (EPMA), Vickers microhardness (HV), and nanoindentation tests. The isothermal treatment at high temperature allowed the formation of both two layers at the reaction zone and a diffusion zone, on the Zircaloy (Zy-4) and the SS-304L sides, respectively. The layers observed on the Zircaloy side consist ε-Zr(Fe, Cr)2 and Zr2(Fe, Ni) intermetallic compounds (IMCs). Those observed on the SS-304L side consist of the α-(Fe, Cr) single-phase and another γ-(Fe, Cr, Ni) + α-(Fe, Cr) mixed part. According to values of microhardness (HV), nanoindentation hardness (H), and elastic modulus (E) obtained from the microhardness and nanoindentation tests, the ε-Zr(Fe, Cr)2 is considered to be extremely hard and brittle; however, Zr2(Fe, Ni) and α-(Fe, Cr) are moderately ductile. [ABSTRACT FROM AUTHOR]

The initial and final melting temperatures of standard, optimized, and modernized zirconium alloy of the E110 type were determined. The stability of zirconium alloys both in terms of composition and phase state during high-temperature heating was secured by preventing contact interaction between the experimental samples and tooling materials. The following melting temperature of the investigated alloys was obtained with maximum error 0.5%: solidus 2116–2121 K, liquidus 2126–2133 K. It was found that iron and oxygen impurities do not affect the melting temperature of the investigated alloys. [ABSTRACT FROM AUTHOR]

We present the characteristics of samples of Zr–1%Nb alloy cut out from fuel cladding tubes saturated with hydrogen. The samples are preliminarily treated, namely, oxidized at T = 580°С and P = 1.33 Pа for τ = 3 h and nitrided at T = 580°C and PN2 = 105 Pa for τ = 9 h. A part of samples was subjected to tensile loading (0.8σT). In the as-delivered state and after oxidation or nitriding, no differences were detected in the character of changes in the curves of hydrogen release in the course of heating as compared with samples loaded (0.8σT) immediately prior to saturation. We established an insignificant increase in the yield limit and ultimate strength of the material with preservation of the level of plasticity of the material. [ABSTRACT FROM AUTHOR]

Alloy blocks with different TiC content were designed, and Mo2FeB2 cermets were prepared by carbon arc surfacing process. The interaction law of TiC content and the microstructure, phase, composition, hardness and wear resistance of the cladding were studied in detail by the combination of experiment and theoretical analysis. On the other hand, the phase transition process of the weldpool is theoretically analyzed by thermodynamic calculation method. XRD test results show that in addition to Mo2FeB2 synthesized in situ, the cladding also forms phases such as TiC, CrB, MoB and Fe-Cr. The number of Mo2FeB2 hard phases gradually increases when TiC content varies from 0% to 15%. The average microhardness of the cladding with 0%, 5%, 10%, and 15% TiC was 992 HV0.5, 1035 HV0.5, 1018 HV0.5 and 689 HV0.5, respectively, with 5% TiC being the largest. Moreover, the cladding with 5% TiC content has excellent wear resistance, which is 14.6 times that of the substrate. [ABSTRACT FROM AUTHOR]

Replacement of conventional Zircaloy fuel cladding with silicon carbide (SiC) fuel cladding is expected to significantly decrease the amount of hydrogen generated from fuel claddings by the reaction with steam during severe accidents. One of their critical issues addressed regarding practical application has been hydrothermal corrosion. Thus, the corrosion resistant coating technology using a Ti-Cr multilayer was developed to suppress silica dissolution from SiC fuel cladding into reactor coolant under normal operation. The effect of radiation on adhesion of the coating to SiC substrate and its microstructure characteristics were investigated following Si ion irradiation at 573 K up to 3 dpa for SiC. Measurement of swelling in pure Ti, pure Cr and SiC revealed that the maximum inner stress attributed to the swelling difference was generated between the coating and SiC substrate by irradiation of 1 dpa. No delamination and cracking were observed in cross-sectional specimens of the coated SiC irradiated up to 3 dpa. According to analyses using transmission electron microscopy, large void formation and cascade mixing due to irradiation were not observed in the coating. The swelling in the coating at 573 K was presumed to be caused by another mechanism during radiation such as point defects rather than void formation. [ABSTRACT FROM AUTHOR]

In this work, Ni-Cr-Mo cladding layers with different Si contents were prepared on Q235 steel using laser-cladding technology, and their corrosion characteristics were investigated in NaCl-KCl-Na2SO4-K2SO4 mixed salt at 550 °C. The corrosion resistance of each cladding layer was tested by weight loss method, and the phase compositions and microstructures of the cladding layers and corrosion products were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that Si contributed to the formation of a dense chromium oxide film on the surface, and the addition of Si can significantly improve the corrosion resistance of the cladding layer at high temperature. At 550 °C, the corrosion rate of the cladding layer with 5 wt.% Si was only 38.2% of that of the cladding layer without Si. After 168 h of high-temperature corrosion, no Cr-rich oxide scale was found in the outermost layer of the Ni-Cr-Mo cladding layer without Si. When Si content was 3 wt.% and 5 wt.%, the Cr-rich oxide scale of the cladding layer was denser than that of the coating with 1 wt.% Si content. [ABSTRACT FROM AUTHOR]

Steam oxidation experiments were conducted at 800–1400 °C with boiling water reactor alloy Zircaloy-2 strip specimens. Sample weight gain measurements were performed on the oxidized specimens before and after the test and were compared to oxygen pickup calculations using the Cathcart–Pawel correlation. The results showed that Zircaloy-2 follows the parabolic law at temperatures above 1000 °C. At or below 1000 °C, the oxidation rate was very low when compared to Cathcart–Pawel correlation and can be represented by a cubic expression. Arrhenius expressions are given to describe the parabolic rate constants at temperatures above 1000 °C and cubic rate constants are provided for temperatures at or below 1000 °C. The weight gains calculated by our Arrhenius correlations are in excellent agreement with the measured sample weight gains at all test temperatures. [ABSTRACT FROM AUTHOR]

The vapor phase chelate delivery (VPCD) technique in conjunction with the modified chemical vapor deposition (MCVD) process is adopted to fabricate fibers with customized doping profiles. The three large‐mode area (LMA) step‐index fibers with different rare‐earth doping profiles in the core region, such as uniform doping, centralized doping, and circumferential doping, are fabricated by optimizing the fabrication parameters. The fibers are tested in a cladding‐pumped amplifier configuration and their output beam qualities and signal‐to‐noise ratio (SNR) are characterized. The investigation reveals that the fiber with centralized doping in the core region exhibits lower M2 compared with the fibers with uniform and circumferential doping, as it has a lower overlap of the higher‐order modes with the doped region. The experimental result is further affirmed through theoretically simulated results. The developed fabrication technique shows potential to fabricate specialty fibers of varied designs, where customized doping profiles are required. [ABSTRACT FROM AUTHOR]

The use of marble as a building or dimension stone is one of the most growing commodities throughout the world. Due to the rapid increase in urbanization, dimension stones are commonly used in building interiors as well as exteriors. Marble, being a metamorphic rock is very desirable to be utilized in structural as well as decorative purposes. The study presented herein evaluates the geotechnical characteristics of the Gahirat marble in the Chitral area, Pakistan. For this purpose, 40 representative samples of the Gahirat marble from ten different vicinities of the Chitral area were collected and tested to determine the correlation amongst the different geotechnical properties of the studied rock. The uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), water absorption, specific gravity, point load strength (PLS), Schmidt rebound hammer, ultrasonic pulse velocity (UPV), and soundness, tests were performed to evaluate the strength of the Gahirat marble for its possible use as a dimension and building stone. An average of 12 measurements for each of the ten rock sample collection vicinities were performed. The statistical analysis shows that a fairly strong linear positive correlation (R2 = 0.80, 0.81, 0.84, 0.92) exists between UCS along with BTS, specific gravity, water absorption PLS and UPV. The maximum values obtained for the 12 measurements regarding the mechanical properties such as UCS, BTS, PLS and Schmidt hammer rebound number were 97.25 MPa, 11.34 MPa, 6.75 MPa and 51, respectively. The maximum values of the physical properties such as water absorption, soundness, specific gravity and UPV tests were calculated to be 0.08%, 0.38, 2.68 and 5.04 km/s, respectively. The results of the uniaxial compressive strength, Brazilian tensile strength, point load strength and Schmidt hammer rebound tests indicate that the Gahirat marble shows high resistance to crushing and bending effects while the specific gravity values indicate its ability to bear the impact of the degree of polishing and grinding. The water absorption and soundness test values indicated that the Gahirat marble is appropriate to be utilized for floor tiles and outdoor cladding due to its resistance against weathering and low rate of the water absorption. [ABSTRACT FROM AUTHOR]

One of the factors capable of resulting in deconfinement of fuel element cladding upon long term storage of spent nuclear fuel (SNF) is reorientation of hydrides. This work estimates the extent of reorientation of hydrates in unirradiated gas filled specimens of fuel element claddings of VVER-1000 reactor (Zr‒1% Nb) under the conditions simulating conditions of dry storage. The specimens with the hydrogen content of 100 and 200 ppm were exposed to thermomechanical tests according to various scenarios at hoop stresses in cladding up to 100 MPa. It has been established that the extent of reorientation of hydrides and related decrease in plasticity of cladding material are insignificant. The most significant factor influencing the extent of reorientation is the level of hoop stresses. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy have been employed for crystallographic and microstructural characterization of nano-precipitates distributed within the α-Zr matrix of the Zircaloy-4 (Zr-4) alloy. These nano-precipitates, typically with an average length between 200 and 500 nm, have been identified as the C16-type Zr2Fe phase. A massive presence of randomly distributed planar defects, including stacking faults and sub-unit cell twins, were detected. Atomic-scale configurations of the intrinsic planar defects in the Zr2Fe nanoparticle phase were investigated, for the first time, through high-resolution TEM analysis. Results show that the stacking faults are extended on (110) planes with a displacement vector of 1 / 4 [ 1 1 ¯ 1 ] . HRTEM observations and electron diffraction patterns acquired by specimen tilting reveal that these twin defects belong to 60° rotation twin with the rotation axis along the [110] direction. Geometric analysis based on the the TEM results reveals that the twinning plane and direction are 1 1 ¯ 2 and [ 3 3 ¯ 2 ] . [ABSTRACT FROM AUTHOR]

The protection of critical infrastructure, including government buildings, airports, religious buildings, military buildings and military vehicles, which are at risk to blast loads, has become important due to increasing terrorist activities in recent years. Sacrificial cladding systems based on negative Poisson's ratio core topologies have recently received more attention as a protective technology due to its excellent energy absorption capability. In this study, field blast tests were performed on metallic re-entrant honeycomb-cored sacrificial cladding systems as protective structures for steel plate structures. This study focused on the near-field blast loading conditions where liquid Nitromethane (NM) spherical charges were detonated in close proximity to the main structure. Two 6 mm thick mild steel plates and two steel plates protected with re-entrant honeycomb-cored sacrificial cladding systems were among the specimens tested. The proposed auxetic cladding system was fabricated from aluminium sheets using a novel in-house built folding machine. Numerical simulations were conducted utilising LS-DYNA software and the Blast Impact Impulse Model (BIIM). The results obtained from the numerical simulations are in good agreement with the experimental results. It was found that the deformation pattern of the sacrificial auxetic cladding system varies with the intensity of the blast loading, and there is a limit at which the proposed protective system ceases to effectively absorb the applied blast loading. The variation of negative Poisson's ratio of the system with blast loading was studied. It was found that the auxetic cladding system could become a solid projectile leading to damage amplification for very close-range blast loads due to rapid densification of the auxetic core. The proposed cladding systems with narrow re-entrant angles performed well under blast loads due to relatively low stiffness of the panels. Finally, the optimisation study was performed for the protective system. Overall, the experimental and numerical results assure that auxetic-based cladding systems are suitable for applications requiring blast protection such as armoured vehicles and critical physical infrastructure but need to be carefully designed for the given blast threat to prevent overloading of the protected structures. [ABSTRACT FROM AUTHOR]

To explore machining parameters for tool wear rate, surface roughness, and material removal rate, Zircaloy-2 was machined with EDM using Cu, CuW and graphite tool. Taguchi L18 Design was used to perform experiments with five independent process parameters (tool material, on-time, off-time, polarity, and current). Response parameters were evaluated and optimized using gray relation analysis and entropy-integrated-gray-VIKOR methods. FESEM was used to observe tool material and oxide layer deposition on machined surface. Maximum material removal rate (1.53 × 10−3 mm3/min) was obtained when the graphite tool with negative tool polarity was used. A confirmation test performed on the optimal factor level process parameters gives an error of 1.9%, 6.4%, and 9.8% for TWR, SR, and MRR respectively. [ABSTRACT FROM AUTHOR]

A multiphase microstructural system of two types of hydrides; f.c.c. δ and b.c.c.. ε hydride precipitates within a parent h.c.p. zircaloy-4 parent matrix were modelled by a crystalline dislocation-density and a finite-element (FE) method that is specialized for large inelastic strains and nonlinear behavior. The different crystalline structure of the hydrides, the parent matrix, and the orientation relationships between the different crystalline phases have been accounted for and modeled with a validated FE approach. The effects of radial hydride factors, hydride volume fraction, hydride morphology, and hydride orientation and distribution on overall behavior were investigated. The predictions provide an understanding of why a distribution of circumferential hydrides have higher strength and ductility than a distribution of radial hydrides. Furthermore, zircaloy δ (f.c.c.) hydride systems have less ductility and strength than the zircaloy ε (b.c.c.) systems. [ABSTRACT FROM AUTHOR]

The use of marble as a building or dimension stone is one of the most growing commodities throughout the world. Due to the rapid increase in urbanization, dimension stones are commonly used in building interiors as well as exteriors. Marble, being a metamorphic rock is very desirable to be utilized in structural as well as decorative purposes. The study presented herein evaluates the geotechnical characteristics of the Gahirat marble in the Chitral area, Pakistan. For this purpose, 40 representative samples of the Gahirat marble from ten different vicinities of the Chitral area were collected and tested to determine the correlation amongst the different geotechnical properties of the studied rock. The uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), water absorption, specific gravity, point load strength (PLS), Schmidt rebound hammer, ultrasonic pulse velocity (UPV), and soundness, tests were performed to evaluate the strength of the Gahirat marble for its possible use as a dimension and building stone. An average of 12 measurements for each of the ten rock sample collection vicinities were performed. The statistical analysis shows that a fairly strong linear positive correlation (R2 = 0.80, 0.81, 0.84, 0.92) exists between UCS along with BTS, specific gravity, water absorption PLS and UPV. The maximum values obtained for the 12 measurements regarding the mechanical properties such as UCS, BTS, PLS and Schmidt hammer rebound number were 97.25 MPa, 11.34 MPa, 6.75 MPa and 51, respectively. The maximum values of the physical properties such as water absorption, soundness, specific gravity and UPV tests were calculated to be 0.08%, 0.38, 2.68 and 5.04 km/s, respectively. The results of the uniaxial compressive strength, Brazilian tensile strength, point load strength and Schmidt hammer rebound tests indicate that the Gahirat marble shows high resistance to crushing and bending effects while the specific gravity values indicate its ability to bear the impact of the degree of polishing and grinding. The water absorption and soundness test values indicated that the Gahirat marble is appropriate to be utilized for floor tiles and outdoor cladding due to its resistance against weathering and low rate of the water absorption. [ABSTRACT FROM AUTHOR]

The enhanced mechanical properties of oxide dispersion-strengthened (ODS) steels are mainly due to the high density of homogeneously distributed oxide inclusions. It is well known that some alloying elements, such as Ti, V, and Al, play an important role in the formation of oxides/nanoclusters and influence the density and size of these inclusions. In this paper, a wide range of ODS steels containing different alloying elements were studied. The microstructural analysis was performed using transmission electron microscopy and atom probe tomography. Different types of inclusions were found in the steels: oxides of the Y–Ti–O or Y–Al–O types with sizes of ~2–15 nm, and nanoclusters (2–5 nm) enriched in Y, O, and Cr, as well as Ti, V, and Al, when these elements were present in the material. It was shown that oxides made the main contribution to the steel strengthening, while the cluster contribution was comparable with that of oxides only in Austenitic ODS and 14Cr ODS steels. [ABSTRACT FROM AUTHOR]

Zirconium alloys are extensively used as cladding material in nuclear reactors. They are vulnerable to hydrogen degradation under the harsh service conditions of the reactors. Optical micrographs taken in some pressure tubes shows the presence of hydride denuded zones closer to the surface, where the hydrides formed in this region are smaller in size compared to the bulk. We investigated the effect of oxygen on diffusivity of hydrogen in α Zr, to check the hypothesis that oxygen slows the diffusion of hydrogen and thereby encourages the occurrence of hydride denuded zones. We used a multi-scale model to simulate H diffusion in Zr with different O concentrations to identify the effect that O has on H diffusivity. From the study we found that oxygen indeed decreases the diffusivity of hydrogen in α Zr for moderate oxygen concentrations. We investigated the diffusion processes of individual H atoms, which showed that the reduction in diffusivity is caused by a decrease in the hopping rates and the formation of hydrogen traps by the combination of several interstitial sites. Though the diffusivity of H seems to be reduced by O, looking at the O concentration profiles found in Zircaloy pressure tubes, we see that the slowing down is insufficient to cause a significant enough change to the size of hydride precipitates. This causes us to reject the hypothesis as the main reason for the formation of denuded zones in Zircaloy pressure tubes. [ABSTRACT FROM AUTHOR]

In this work, samples of zirconium alloys Zr1Nb and Zircaloy-4W were subjected to two-stage oxidation experiments – at first in H216O solution and then in H218O steam. Raman spectroscopy was used to analyse distribution of 18O isotope in corrosion layers of the alloys. Layered distribution of 18O was observed in case of Zr1Nb samples; Zircaloy-4W had 18O present only at metal/oxide interface. This observation is attributed to differing kinetic transitions, which influence transport of oxygen through oxide layer. [ABSTRACT FROM AUTHOR]

Plastic instability of mechanical bulging process, different from the traditional tube hydroforming, is developed for Zircaloy tube based on localized necking criterion. Based on the observation of published experiments of bulging, an elementary analyzed model of plastic deformation is proposed and applied for examining the variation of bulging process and its limitation. The developed model comprises two deformation regions, one is bulged part with friction effect and the other is flattened part but without friction effect. All mentioned process parameters, such as contact friction, material properties (strain hardening exponent and normal anisotropy), and process geometries conditions (tube radius and thickness), are taken into account for in such mechanical bulging model. Plastic instability in bulging is examined using localized necking criterion based on the proposed model. A published experiment was initially used to verify the present model. Then, the effects of process parameters on the variation of bulging limit are investigated. The developed model allowed us to better understand the failure mechanism through the localized necking criterion, and also can be defined as a sign of fracture for a bulged tube. Moreover, a proposal will be made to examine the limitation of bulging for practical needs. [ABSTRACT FROM AUTHOR]