Showing papers on "Zirconium alloy published in 1993"

Dual composition coupler for modular medical implants

Abstract: The invention provides an interpositional coupler for inserting between modules of a modular medical implant, wherein the modules are fabricated of compositions having different electrochemical potentials, to reduce or prevent the flow of a galvanic current and thereby reducing or preventing this contribution to corrosion of the prosthesis. The coupler may be of an insulative type comprising a zirconium/zirconium alloy core coated with blue-black zirconium oxide or nitride or any metal coated with amorphous diamond-like carbon. Alternatively, the coupler may be of a dual composition type with each of the compositions having essentially the same electrochemical potential as the module to which it couples.

Determination of the zirconium site in zirconium‐substituted Nd2Fe14B

Abstract: We report a direct determination of the Zr site in pseudoternary alloys with a nominal composition of Nd1.6Zr0.4Fe14B using extended x‐ray absorption fine structure (EXAFS). Comparing the Zr EXAFS from these alloys to the Y EXAFS from Y2Fe14B and the Fe EXAFS from Nd2Fe14B reveals that the local Zr and Y environments are nearly identical, and quite disparate from the Fe environment. This finding, and results from x‐ray diffraction and electron microscopy, lead to the conclusion that Zr is incorporated as a substituent for Nd in the Nd2Fe14B structure.

Self-consistent calculation of steady-state creep and growth in textured zirconium

Abstract: Irradiation creep and growth in zirconium alloys result in anisotropic dimensional changes relative to the crystallographic axis in each individual grain. Several methods have been attempted to model such dimensional changes, taking into account the development of intergranular stresses. In this paper, we compare the predictions of several such models, namely the upper-bound, the lower-bound, the isotropic K∗ self-consistent (analytical) and the fully self-consistent (numerical) models.

Grain-growth in nanocrystalline zirconium-based alloys

Abstract: Crystallization and subsequent grain growth in nanocrystalline Fe33Zr67 and (Fe, Co)33Zr67 alloys were studied by TEM, differential scanning calorimetry and X-ray diffraction. The grain-growth data for both alloys obtained over a wide temperature range (about 200 °C) were fitted to different kinetic equations (with different grain-growth exponent, n). The model with n=3 (Equations 4 and 5) was found to predict in the best way the isothermal experimental data. This result gives strong evidence that crystallization (in our case by a polymorphic reaction) is indeed observed of a glass into a nanocrystalline material prior to the coarsening, rather than grain growth in an extremely fine-grained material which was never glassy at all. The activation energies for grain-growth, — 260±25 kJ mol−1, were found to be practically the same for both systems. Additional information about the crystal growth kinetics of the nanocrystals in the amorphous matrix was obtained for (Fe, Co)33Zr67 glass.

Method for making fuel cladding having zirconium barrier layers and inner liners

Abstract: The present invention provides a cladding having an outer circumferential substrate, a zirconium barrier layer metallurgically bonded to the inside surface of the substrate and an inner circumferential liner metallurgically bonded to the zirconium barrier The inner circumferential liner is more ductile than conventional Zircaloy The low ductility of the inner circumferential liner is obtained by using a zirconium alloy containing a low tin content (eg less than 12% by weight) and/or a low oxygen content (eg less than 1000 ppm) The inner circumferential liner is less than about 25 micrometers thick

Manufacture of zirconium cladding tube with internal liner

Abstract: A method of manufacturing nuclear fuel elements comprising fuel rods whose cladding tubes are provided with an internal liner layer to obtain PCI resistance in the nuclear fuel element comprises carefully choosing parameters for heat treatment of the inner component even from the machining of an ingot of the inner component. The internal layer of zirconium or a zirconium alloy suitable as inner layer in a PCI-resistant cladding is manufactured, from the fabrication of an ingot of the inner component up to the completion of a cladding tube, comprising forging, rolling, extrusion, heat treatment and final heat treatment, in such a way that the temperature in the inner component never exceeds the temperature when an incipient phase transformation to beta phase takes place.

Effect of Beta Heat Treatment on Microstructure and Nodular Corrosion of Zircaloy-4

Abstract: The effect of β-heat treatment on microstructure and nodular corrosion of Zircaloy-4 were investigated for the specimens which were β-heat treated and then cooled in various cooling process, such as, iced brine, water, oil, air, and furnace cooling. It was observed that the martensitic structure with substructures of dislocations as well as twins is formed at the cooling rate of 2,100°C/s, whereas at the cooling rate of l,200°C/s the classical Widmanstatten structure appears with dense dislocations in a lath and precipitates along the lath boundary. The transformation in the water quenched specimens was suggested to take place by both diffusion- and diffusionless transformation process. The nodular corrosion behavior was investigated at steam of 500°C and 10.3 MPa. The corrosion resistance of the β quenched specimens decreased with the decrease in the cooling rate so that the furnace cooled specimens exhibit the worst corrosion resistance, resulting in nodular corrosion. The corrosion of the furn...

High-strength powder metallurgy aluminum alloys in glass-forming AlNiCe(Ti or Zr) systems

Abstract: Powder metallurgy (P/M) aluminum alloys with high mechanical strengths have been developed by taking advantage of rapid solidification (RS). The improved strengths result from structural modifications such as reduction of segregation, refinement of grain size and increase in solid solubility limit which mainly depend on the amount of undercooling of melt. To produce crystalline alloys with a refined structure, few approaches are considered: the crystallization of an amorphous alloy, the control of cooling rate from melt and the selection of optimum composition for glass-forming alloys. However, these methods are generally attended with a disadvantage for embrittlement. Recently, it has been found that Al-based amorphous alloys exhibiting high tensile strength and good bending ductility form by liquid quenching in the Al-Ln-TM (Ln: lanthanide metal, TM: transition metal) system. Furthermore, the consolidation of the amorphous alloy powders to a bulk amorphous alloy has also been achieved by warm extrusion. The first aim of this paper is to examine the effect of alloy composition on the strength and ductility of crystalline compacts produced by extrusion of rapidly solidified powders in the Al-Ni-Ce-TM(TM:Ti, Mn, Fe, Co, Cu, Zr) systems where an amorphous phase is formed by melt spinning. The second is to investigate whethermore » or not the structural refinement by using glass-forming alloys is useful to develop high-strength P/M aluminum alloys.« less

The thermal ratchetting of hydrogen in zirconium-niobium — An illustration using finite element modelling

Abstract: It was recognized early in DHC (Delayed Hydride Cracking) studies in zirconium alloys that crack initiation could often be induced by heating the sample above the test temperature and cooling it back down. Additionally in many cantilever beam test studies of DHC initiation, the samples were routinely thermally cycled once a week from test temperature to room temperature, then to 50[degree] above the test temperature and then back to the test temperature as a means of simulating' the start-up shut-down cycles of real pressure tubes in reactors. Crack initiation often occurred during these cycles. In spite of this little has been done to explain why thermal cycling should be effective in aiding hydride formation at the crack tip. In this paper the way in which thermal cycling can cause large increases in the hydride formation at the peak stress locations will be discussed and the mechanisms illustrated with the aid of a finite element model. Since the thermal cycle can affect the hydrogen concentration near a stressed crack in the same way that a ratchet gear affects mechanical rotation it has been called a thermal ratchet.

Zirconium alloy with tin, nitrogen, and niobium additions

Abstract: The alloy of the present invention features controlled amounts of tin, nitrogen, and niobium and includes tin (Sn) in a range of greater than 0 to 150 wt %, wherein 06 wt % is typical The alloy also has iron (Fe) in a range of greater than 0 to 024 wt %, and typically 012 wt %; chromium (Cr) in a range of greater than 0 to 015 wt % and typically 010 wt %; nitrogen (N) in a range of greater than 0 to 2300 ppm; silicon, in a range of greater than 0 up to 100 ppm, and typically 100 ppm; oxygen (O) in a range of greater than 0 and up to 1600 ppm, and typically 1200 ppm; niobium (Nb) in a range of greater than 0 wt % to 05 wt % and typically 045 wt %; and the balance zirconium

Hydriding of zirconium alloys in hydrogen gas

Abstract: Zirconium alloys were hydrided by exposure to hydrogen gas at pressures up to 13.6 MPa in an autoclave maintained at 350 °C for 10 h. Hydrogen uptake was found to increase with applied hydrogen pressure. Surface oxide was found to inhibit hydrogen uptake; hydrogen uptake measurements and hybride morphologies of the specimens confirm that the rate of hydrogen uptake is controlled by the oxide. Under test conditions, at known temperature and pressure, the 10 h exposure was sometimes insufficient for uniformly distributed hydride formation. A layer of relatively high hydride concentration near the specimen surface was produced. A method for charging mechanical testing specimens, which exploits the uptake rate control by the oxide film, is proposed.

A strong ceramic based on aluminum oxide and zirconium dioxide

Abstract: The theoretical premises and experimental results on fabrication of ceramics based on aluminum oxide with a regulatable structure which ensures high strength properties and the possibility of wide use in different areas of technology were reported. The effect of adding zirconium oxide to aluminum oxide on the structure and strength properties of the ceramics was demonstrated. New ceramic materials having a high strength were developed with highly disperse powders. The technological parameters of corundum ceramics of the “Koral” type and materials from mixtures of zirconium dioxide and aluminum oxide containing tetragonal and cubic solid solutions based on zirconium dioxide were developed. Stable results were obtained for the strength properties of ceramics made of special-purity tetragonal zirconium dioxide.

Amorphous zirconium alloy having wide region of supercooled liquid

Abstract: PURPOSE:To provide an amorphous Zr alloy having a wide region of a supercooled liq. CONSTITUTION:This amorphous Zr alloy has a compsn. represented by a formula Zr1000-a-b-c-dMaCubNicBed (where M is Al and/or Ti, 5 =120K region of a supercooled liq. represented by an equation DELTAT=Tx-Tg (where Tx is crystallization temp. and Tg is vitrification temp.). This alloy is especially excellent in secondary workability because of a wide region of a supercooled liq. and a large-sized amorphous product can be produced because of high amorphous phase forming ability.

Nuclear fuel rod and method of manufacturing the cladding of such a rod

Abstract: A nuclear fuel rod cladding for a water moderated and nuclear reactor comprises an inner portion of Zircaloy 4 and an outer portion of a zirconium-based alloy which contains by weight, besides zirconium and unavoidable impurities: 0.35% to 0.65% tin 0.18% to 0.25% iron 0.07% to 0.13% chromium, and 0.19% to 0.23% oxygen, with the sum of the iron, chromium, tin, and oxygen contents being less than 1.26% by weight. It may alternatively or additionally comprise 0.80% to 1.20% by weight niobium and then the oxygen content is in the range 0.10% to 0.16% by weight. The thickness of the outer layer is 10% to 25% of the total thickness of the cladding. In a modification, up to 0.5% of iron, chromium, niobium is replaced by an equivalent content of vanadium.

Poisoning and saturation of St 737 getter alloy in the conversion of isotopic waters to isotopic hydrogen

Abstract: The results of the studies performed to investigate the saturation capacity of St 737 getter alloy (Zr[V 0.5 Fe 0.5 ] 2 ) in its application for conversion of water to hydrogen and the functional behaviour of the conversion reaction rate with large oxygen concentration in the alloy are reported. The experiment was performed with the getter alloy at a temperature of 400°C. The conversion process was monitored by two independent techniques — (i) by the hydrogen release, using a quadrupole mass spectrometer and (ii) by the quantity of water reduction in liquid phase. It was found that more than 100 mg of water was converted and 13 Pa m 3 of hydrogen was released by a gram of alloy. A chemical analysis of the alloy performed after the experiment showed that the oxygen content in the alloy was about 7% by weight. The post-experiment diffraction analysis of the alloy showed that the crystalline structure of the alloy is almost completely destroyed and that the oxides formed are essentially amorphous. A brief discussion of the significance of the results for the application to tritiated water handling in future fusion reactions is also given.

Rugged electrode for electrochemical measurements at high temperatures and pressures

Abstract: A high temperature-high pressure electrode for electrochemical potential measurement has a high temperature probe comprising an oxidized zirconium alloy tube member having an electroconductive core which includes a liquid electrolyte and a porous plug held in place by an oxidized zirconium alloy tube and end plug with an axial bore extending therethrough. The electroconductive core can comprise a liquid electrolyte of soaked zirconia sand and a second porous plug. In another embodiment, the zirconia sand is replaced by a surface oxidized zirconium alloy rod with grooves which extend between ends for containment of the liquid electrolyte. This embodiment also contains a second porous plug. In a modification of the latter embodiment, there is a bore in the proximal end of the surface oxidized rod which communicates with the grooves to provide electrical continuity. A Teflon sleeve forms an annular seal between the proximal end of the oxidized rod and the oxidized tube.

The ductile-brittle transition of a zirconium alloy due to hydrogen

Abstract: Zircaloy-4 is generally used as fuel element cladding and an in-core structure c'm~cn..~t in light water reactors. Its mechanical properties are degraded by the presence of hydrid ~a wh ch are primarily formed by the absorption of excess hydrogen from the corrosion reaction: Zr + 2H20 ZrO 2+ 2H 2 [1]. Lin et el.[2] and Baiet el. [3-5] studied the mechanical properties of hydri.l~ Z£rcaloy-4 alloys independently by tensile testing the smooth specimens. Both of them obser,ed a room temperature ductile-brlttle transition on the reduction of area, when the hydrogen content in the specimen is higher than some critical value. Their deflnltion of "ductile-brittle transition" is the abrupt change of the value of reduction of area, which is somewhat different from the conventional definition determined from impact tests. Since the effect of hydrogen on reduction of area 18 more distinct than on elongation, the reduction of area has been used as a parameter to exhibit hydrogen effect. Although reduction of area Is not a standard parameter for a notched specimen geometry, it can be used as a relative criterion for judging the ductility of a specSmen being tensile teated. In thl8 paper we followed the definition of Lin and Bai. The observations of ductile-brittle transitions mentlonedsboveweremostlyperformedusingmmooth tensile specimens in standard tensile tests. Since notched specimens provide a triax£al state of stress, which will enhance brittle fracture, they are more suitable to be used to study the ductile-brittle transition of metals than smooth tensile specimens. In the present study, notch tensile tests were performed on Zircaloy-4 alloys at various temperatures up to 300"C in hydrided conditions to investigate the change of ductile-brittle transition due to notch effe.:t. Additionally, no previous study has been done on Zircaloy-4 alloy to determine whether -he ductile-brittle transition is existed in a hydrogen gas environment. To determine this phenomenon, notched, uncharged Zircaloy-4 specimens were tensile tested in a hydrogen ~as environment at various temperatures up to 200°C. We found that the ductile-brittle transition oxlsts not only for the hydrided Zircaloy-4 but also for Zircaloy-4 tested in the hydrogen gas environment. The specimen materials were commercial Zircaloy-4 purchased in plate form. The chemical compositions are listed in Table I. All specimens were used in the as-recelved condition, annealed at 760"C for one hour and air cooled. The grain shape was equiaxed and the grain sizes wore 15 ~m and i0 pm for specimens A and B, respectively. The yield strengths for specimens A and B were 484 MPa and 435 MPa, respectively. Specimens A (2 mm thickness) with dimensions 150 mm x 25 nm x 2 on were hydrided and then tensile tested in air. Specimens B (1.6 mm thickness) with dlmenslons 75 mm x 25 ~ x 1.6 ~ were tensile tested in hydrogen gas. All the specimens wore out transverse to the rolling direction. A saw cut (about 7 mm deep, notch root radi .s abf,ut 0.125 mm) was made in the middle of one edge of each specimen. For the hydrlded apeclmL~ns, the material was gaseously hydrided at 350"C in an autoclave at various pressures for different durations. The hydrlding procedures are described elsewhere [6]. After charging, the hydride morphology was examLned using an optical microscope. For each specimen, after testing, sectluns near the fracture surface were cut off to determine the hydrogen content using the inert gas fusion method at 1800°C. For those tests performed in hydrogen gas, specimens were sealed in an autoclave. The autoclave system was evacuated down to 6.67 Pa using a mechanical pump, then flushed with argon gas to ambient pressure, and evacuated again. The autoclave was then at least twice flushed with hydrogen to ambient pressure end evacuated. Finally, hydrogen was admitted up to experimental pressure. The hydrogen pressures used Ln this study were 101, 1010 and 2020 kPa. High purity hydrogen with H 2>99.9995% was used. The tensile tests wore carrled out at room temperature (25"C), 100", 200 ° , and 300"c (only for hydrided specimens) on a constant extension rate testing machine (CERT) at a cross-head speed of 3 x 10-'m/sec. The time for a single test lasted from seven hours to twelve hours,depending on the hydrogen content, hydrogen pressure or experimental temperature. In general, as the hydrogen content, hydrogen pressure, or exp~-rlmental

Nuclear reactor clad fuel tube superior in corrosion resistance and its production method

Abstract: PURPOSE:To provide a clad fuel tube superior in corrosion resistance and resultingly having a long life and its proper production method CONSTITUTION:On the outer surface of inner layer of a reactor clad fuel tube formed out of a zirconium-based alloy, the outer layer is coated by forming an anti-corrosion metal superior in corrosion resistivity to the zirconium-based alloy For the anti-corrosion metal, Ti or titanium-based allopy is preferable The production method for the cladding is as follows; on an inner layer materal formed with a zirconium base alloy, a composit material coated with an outer layer material formed with Ti or a titanium-based alloy superior in corrosion resistance to the zirconium-based alloy is hot-worked with a reduction ration of 5% or more within a temperature range of 500 to 850 degC