Zr Specimens Research Articles

The investigation of selected NpZr alloys by X-ray diffraction up to 700 °C

High temperature X-ray diffraction analysis of two NpZr (25 and 33 at.% Np) binary alloy specimens prepared by arc melting was performed to help elucidate important features of the NpZr phase diagram, several features of which have not been resolved. Temperatures in these studies ranged from 25 to 700 °C. The NpZr specimens were characterized as consisting of different combinations of Np, Zr and NpZr2 phases at the different temperatures. The results obtained for this Zr-rich portion of the phase diagram diagram suggest that there is not a continuous mutual solubility between γ-Np and β-Zr, as known to exist in the UZr binary system. The solubility of Zr in γ-Np was estimated to be ca. 4% at 600 °C. Only the α form of Zr was observed in these studies, indicating that there was insufficient Np dissolved in the Zr phase to stabilize its β phase below the normal α-β transition temperature of 850 °C. The hexagonal NpZr2 was detected up to 550 °C; above this temperature it appeared to decompose. Diffraction lines for the α, β and γ forms of Np were observed as a function of the temperature. Diffraction lines for Np disappeared above 650 °C, presumably because of its “localized” melting in micro-domains.

Differential Thermal Analysis of Solid Zirconium

Abstract Several observations are made in the differential thermal analysis (DTA) test of solid zirconium (Zr) specimens. It is found that an increasing heating rate generally increases the solid-phase transition temperature for both nondeformed and cold-worked specimens, but to a different extent. Upon cycling the specimen with a constant heating rate, the phase transition temperature decreases initially during the first few runs and then remains constant. Also, holding a specimen for some time just before the phase transition during heating increases the phase transition temperature. Specimen heating history and prior cold work are also found to influence the solid-phase transition temperature.

α-Zr self-diffusion anisotropy

Self-diffusion coefficients ( D) have been measured in nominally pure (NP) α-Zr single crystals (= 50 ppm Fe) in the range 867–1107 K, in directions either parallel (Dpa) or perpendicular ( D pe) to the c-axis. Measurements were also made on high-purity (HP) α-Zr single crystals (< 1.0 ppm Fe) at 1110 K. The diffusion profiles were determined by sectioning and radio-tracer ( 95 Zr) counting. Sectioning was done with a sputtering device, or a microtome (some NP experiments at 1107 K). D values for NP Zr are about an order of magnitude higher than the corresponding values for HP Zr. Diffusion anisotropy is complicated. The sputter-sectioned NP Zr specimens show increasing anisotropy ratios (AR = Dpa/Dpe), from 1.0 to 3.2, with decreasing temperatures, whereas AR = 0.53 for both the microtome-sectioned NP and sputter-sectioned HP Zr: the low AR value is consistent with expectations based on intrinsic self-diffusion in hcp metals with c/a < 1.633.

Diffusion of copper and silver in zirconium

B.c.c. zirconium (/3-Zr) is one of the well-known anomalous b.c.c, metals, which show a significant upward curvature in the Arrhenius plot of the self-diffusion coefficients [1]. H.c.p. zirconium (cr-Zr) also shows peculiar self-diffusion behaviour, i.e. downward curvature in the Arrhenius plot [2]. Furthermore, it is well known that impurity atoms with small size such as Fe and Co are fast diffusers in both fl-Zr [3] and cr-Zr [3]. However, according to a recent compilation of a vast amount of experimental data on diffusion in solid metals and alloys [4], a large scatter in the diffusion parameters (the preexponential factor Do and the activation energy Q) for impurity diffusion of some elements in/3-Zr and ol-Zr is reported. For example, the values of the activation energy for the diffusion of Ag in o~-Zr by various researchers lie in a wide range between 174 and 245 kJ mol -I, all of which have been obtained by the radiotracer method. Thus, use of another experimental method may be helpful to elucidate the diffusion behaviour. On the other hand, no data on the diffusion of Cu in/3-Zr have been compiled [4]. The atomic radius of Ag (0.1406 nm) is larger than that of Cu (0.1244 nm) but smaller than that of Zr (0.1558 nm) in the b.c.c, structure [5]. Thus, diffusion experiments of Cu and Ag in Zr are effective for confirming the size effect for the impurity diffusion. In the work reported here, interdiffusion experiments with couples of pure Zr and dilute binary alloys containing Cu and Ag were carried out. The impurity diffusion coefficients of Cu and Ag in Zr were determined by applying Darken's relation [6], i.e. the extrapolated value of the interdiffusion coefficient to the infinite dilution of the solute can be regarded as the impurity diffusion coefficient of the solute in Zr. This method avoids problems such as chemical reaction on the surface of reactive Zr specimen that occur with the radiotracer diffusion experiments. A pure Zr rod 7 mm in diameter was made by Ar arc melting of Zr sponge of 99.6% purity supplied by Nippon Mining Co. Ltd. The main impurities in this material were (ppm): 852 O, 393 Fe, 38 Mg, 100 Cr, <60 Si and <50 Hr. The grain size in the rod was 1-2 mm. The Zr rod was cut to make disc specimens 5mm in thickness. Rods of Zr-1.57 at% Cu, Zr-0.34 at % Ag and Zr l .27 at % Ag alloys were made by Ar arc melting of the pure Zr sponge with Cu oxygen-free chips of 99.99% purity and Ag

Composition and structure of zirconium implanted with nitrogen at high fluence

High-fluence implantations of 100 keV N 2 + ion into a zirconium layer deposited by an electron beam were carried out at room temperature and at liquid-nitrogen temperature with and without nitrogen gas of a pressure of 1 × 10 −4 Torr. Depth profiles of atom concentrations were determined by Rutherford backscattering spectrometry, Auger electron spectroscopy, and resonance nuclear reaction analysis. The experimental results were compared with the theoretical results obtained by Monte Carlo simulations of the dynamic-SASAMAL code. The depth profiles measured by RBS agreed well with the calculated profiles for all fluences from 1 × 10 17 to 5 × 10 17 ions/cm 2, but differed from those obtained by AES indicating the existence of easily released nitrogen in the Zr specimen implanted with nitrogen at high fluence. Glancing angle X-ray diffraction was used to confirm zirconium nitride formation.

Solute diffusion in α-Zr: Rutherford backscattering and secondary-ion mass spectrometry study

Abstract Substitutional diffusion coefficients D of Hf, Ta and Pb have been measured α- Zr single crystals and the diffusion profiles analysed by Rutherford backscattering (Hf, Ta and Pb) and secondary-ion mass spectrometry (Hf). Measurements were made either parallel (D ‖) or perpendicular (D‖ ) to the specimen c axis. Although the main study is concerned with the influence of Fe on the diffusion of Hf, Ta and Pb at 1100 K, some preliminary data are also reported for Pb and Ta at 872 and 1000 K. The initial measurements at 1100 K show that D(Ta)>D(Hf)>D(Pb); the Zr specimens used for these measurements were then treated to reduce the Fe content (65–30 at.p.p.m.) and the diffusion coefficients remeasured. With one exception, D‖ for Hf, the diffusion coefficients fell by a factor of about two with the decrease in Fe concentration; D‖ for Hf fell by about an order of magnitude. All the D values measured at 1100 K for Hf, Ta and Pb lie in the range 4 × 10−19-3 × 10−17m2s: those for Hf, and their dependence on the Fe concentration (with the exception of the low-Fe D datum), are notably similar to α-Zr self-diffusion values presented in a very recent study. Together, the results are considered in terms of intrinsically normal diffusion with enhancement of the more slowly diffusing species by an Fe-associated defect. A comparison of solute D values measured in α-Zr, where Fe levels have not been deliberately reduced, shows that substitutional solute diffusion increases with decreasing size and valence.

Anisotropic distribution of dislocation loops in HVEM‐irradiated Zr

Abstract Specimens of Zr have been electron-irradiated at temperatures of ∼715 K using a 1 MeV electron microscope. The damage structure has been analysed at room temperature, and the results show that interstitial and vacancy loops with b = ⅓〈1120〉 nucleate and grow. In addition, vacancy loops with b = ½[0001] and interstitial loops with b = ⅓〈1123〉 are observed in foils having normals N close to [0001] and 〈1210〉, respectively. There is a partitioning in the Burgers vecctor of all loops such that vacancy loops generally tend to have b as nearly parallel as possible to N, and interstitial loops tend to have b perpendicular to N. This effect is most marked for c component loops and is related to a tensile stress generated in the plane of the foil during oxidation of thin foils. These observations are discussed in terms of irradiation-induced growth.

Self-Ignition of a porous metal plate in an oxidizing atmosphere

1. A formula is proposed for calculating the critical self-ignition temperature of a porous metal plate in an exothermic oxidation reaction obeying a parabolic law. 2. Experiments with Zr, Hf, and Ti specimens carried out with the aim of verifying the critical selfignition temperature formula yielded values showing good agreement with calculated T0 values.

Time-Resolved Spectroscopy of Laser-Initiated Metal Combustion

A rapid-scan spectrometer employing a silicon-target vidicon detector was used to study the time-resolved emission spectra of laser-ignited metals. Bulk specimens of Ca, Mg, Zr, Ti and several Ti alloys were ignited with a 90 W cw CO2 laser in air or under a gentle flow of oxygen. Line and band emissions observed between 300 and 1100 nm during combustion help to identify vapor phase reactants and products and their locations in the flame. Disappearance of discrete spectra during the transient combustion of Ti and Zr gives information on the accumulation of molten oxide products. Observations of the continuum radiation emitted by laser-irradiated flames indicate a laser-stimulated luminescence from condensed metal oxide particles.

Determination of the Optical Constants of Uniaxial or Isotropic Metals by Measurement of Reflectance Ratios*

A method is described for determining the optical constants of uniaxial cyrstals, or isotropic specimens, from measurement of the relative flux of light reflected at three angles of incidence. Only a single, fixed, polarizer is required. The optical constants of single crystals of Cd, Mg, and white Sn, and polycrystalline specimens of Cr, Hf, Ni, and Zr, within the range 2 to 5.6 eV, are presented and briefly discussed. Energy-loss functions are given for Cd, Mg, and white Sn. For some of these metals the new results are compared with those obtained previously using the ellipsometric technique.

Zr表面の酸化被膜の構造

The present authors have studied the structure of thin oxide films formed on the Zr surface under various conditions. The following results were obtained by electron microscopy and electron diffraction. (1) The oxide films formed by dry oxidation, e.g., heating in air at 300°∼500°C or dipping in a fused salt bath (NaNO3 50 g, KNO3 50 g, MnO2 1 g: 400°C), consisted of only the monoclinic ZrO2. (2) A number of regularly aligned lines of about 2500 Å in length was observed in some oxide films formed on the surfaces smoothed by cloth-polishing. (3) The tetragonal ZrO2 as well as the monoclinic ZrO2 was detected in the Zr oxide films produced by wet oxidation such as immersing in boiling conc. HNO3. (4) On the hydrogen-absorbed surfaces by either cathodizing in 5%H2SO4 or immersing in 35%HCl, the oxide films composed of the tetragonal and the monoclinic ZrO2 crystals were produced by dry oxidation. (5) When the Zr specimen was quenched in water after heating in air at 400°C, the surface was covered with both the tetragonal and the monoclinic ZrO2 crystals. (6) The tetragonal ZrO2 in the oxide films produced by wet oxidation transformed to the monoclinic ZrO2 by heating in air at above 1150°C. (7) These results indicate that the meta-stable tetragonal ZrO2 crystals are produced in the oxide films partly due to the existence of water or hydrogen in oxidizing atmosphere.

Excitation of Characteristic X Rays by Protons, Electrons, and Primary X Rays

Protons, electrons, and primary x rays were used to excite characteristic x radiation from individual specimens of Ti, Cr, Fe, Cu, Ge, Zr, and Au. X-ray yield expressed as (photons /sr)/ quantum increased with quantum energy in a similar manner for protons in the range about 1 MeV and electrons in the range about 50 keV. For primary x-ray excitation, the yield decreased with increasing quantum energy, a relationship opposite to that for proton or electron excitation. It appears that the relative values of photo-electric absorption and scattering must be quite different for x rays and electrons to account for their opposite relationship of yield vs energy.

The effect of nitriding on the elevated temperature tensile properties of some molybdenum-base alloys

The elevated temperature tensile properties of Mo-0.49% Ti, Mo-0.98% Ti and Mo-1.5% Zr specimens, in both the dispersion-hardened and the recrystallised conditions, have been investigated between room temperature and 900°C using two strain-rates. The effect of increase in temperature and in strain-rate on ultimate tensile stress (U.T.S.) and ductility have been studied and metallographic and fractographic observations have been made on the tested specimens. The results are discussed in the light of current theories of elevated temperature deformation and intergranular failure.

The Effect of Electrolyte Composition on the Anodic Oxidation of Zirconium

not Available.