Showing papers on "Zirconium alloy published in 1997"

Bulk amorphous alloys with high mechanical strength and good soft magnetic properties in Fe–TM–B (TM=IV–VIII group transition metal) system

Abstract: New bulk amorphous alloys exhibiting a wide supercooled liquid region before crystallization were found in Fe–(Co,Ni)–(Zr,Nb,Ta)–(Mo,W)–B systems. The Tg is as high as about 870 K and the supercooled liquid region reaches 88 K. The high thermal stability of the supercooled liquid enabled the production of bulk amorphous alloys with diameters up to 6 mm. These bulk amorphous alloys exhibit a high compressive strength of 3800 MPa, high Vickers hardness of 1360, and high corrosion resistance. Besides, the amorphous alloys exhibit a high magnetic-flux density of 0.74–0.96 T, low coercivity of 1.1–3.2 A/m, high permeability exceeding 1.2×104 at 1 kHz, and low magnetostriction of about 12×10−6.

Laves intermetallics in stainless steel–zirconium alloys

Abstract: Laves intermetallics have a significant effect on properties of metal waste forms being developed at Argonne National Laboratory. These waste forms are stainless steel-zirconium alloys that will contain radioactive metal isotopes isolated from spent nuclear fuel by electrometallurgical treatment. The baseline waste form composition for stainless steel-clad fuels is stainless steel-15 wt.% zirconium (SS-15Zr). This article presents results of neutron diffraction measurements, heat-treatment studies and mechanical testing on SS-15Zr alloys. The Laves intermetallics in these alloys, labeled Zr(Fe,Cr,Ni){sub 2+x}, have both C36 and C15 crystal structures. A fraction of these intermetallics transform into (Fe,Cr,Ni){sub 23}Zr{sub 6} during high-temperature annealing; the authors have proposed a mechanism for this transformation. The SS-15Zr alloys show virtually no elongation in uniaxial tension, but exhibit good strength and ductility in compression tests. This article also presents neutron diffraction and microstructural data for a stainless steel-42 wt.% zirconium (SS-42Zr) alloy.

Thermal and Magnetic Properties of Fe 56 Co 7 Ni 7 Zr 10− x Nb x B 20 Amorphous Alloys with Wide Supercooled Liquid Range

Abstract: Amorphous alloys with a wide supercooled liquid region of 45 to 85 K were found to be formed in Fe 56 Co 7 Ni 7 Zr 10-x Nb x B 20 (x= 0 to 10 at%) alloys by melt spinning. The glass transition temperature (T g ) and the crystallization temperature (T x ) increase by the dissolution of 2 to 4%Nb. The degree of increase is larger for T x than T g , leading to the maximum ΔT,(= T x - T s ) of 85 K for the 2%Nb alloy. The ΔT x value is about 20 K larger than the largest value for the newly developed Fe-(AI, Ga)-(P, C, B, Si) amorphous alloys. The crystallization occurs through a single stage, amorphous→α-Fe+y-Fe+Fe 2 Zr+Fe 16 Nb 6 +B 18 , for the alloys containing less than about 6%Nb and through two stages, amorphous→amorphous+y-Fe→γ-Fe+Co 3 Nb 2 B 5 +Ni g Nb, for the alloys containing more than 8%Nb. The change in the crystallization process for the Nb-rich alloys probably reflects the disappearance of Fe 2 (Nb, Zr) precipitates because of the weaker bonding of Fe-Nb pair as compared with Fe-Zr one. As the Nb content increases, the saturation magnetization (I s ) and permeability (μ e ) of the annealed alloys decrease while the coercive force (H c ) remains almost unchanged. The good soft magnetic properties are obtained for the alloys containing less than 2%Nb subjected to annealing for 300 s at 800 K and the I s , H c and μ e at 1 kHz are 0.96 T, 2.0 A/m and 19100, respectively, for the 0%Nb alloy and 0.75 T, 1.1 A/m and 25000, respectively, for the 2%Nb alloy. The success of synthesizing the new amorphous alloys with a wide supercooled liquid region more than 80 K and with good soft magnetic properties is promising for future development as soft magnetic bulk amorphous alloys.

Mechanical behavior of nanocrystalline aluminum-zirconium

Abstract: An investigation of the room-temperature mechanical properties and deformation behavior of nanocrystalline aluminum-zirconium has been conducted via microhardness, nanoindentation and novel tensile experiments. Nanocrystalline specimens were produced by the inert-gas condensation process with electron beam evaporation. The modulus of elasticity of nanocrystalline Al-Zr was determined to be similar to that of coarse-grained aluminum. The hardness, strength and ductility of the samples, however, were found to be strongly impacted by grain size, which is reduced at higher zirconium levels. Extremely high hardnesses were obtained for the materials (up to ~ 3 GPa), while the tensile strengths were less impressive. Some ductility in tension was exhibited by specimens with relatively large grain sizes (≥ 100 nm), although the elongation to failure dropped to less than 1% when the grains were stabilized to ~ 10 nm by zirconium additions. This behavior appears to be linked to the increasingly high stresses required to generate dislocations to prevent crack propagation and cause yielding as the grain size is reduced into the nanometer regime. At room temperature and at the strain rate employed in this study (10−4 s−1), no evidence was found to suggest that an alternative, diffusional-based deformation mechanism takes over at the smallest grain sizes.

Effects of test temperature, grain size, and alloy additions on the cleavage fracture stress of polycrystalline niobium

Abstract: The current work investigates the effects of test temperature (77 to 131 K), grain size (63 to 165 µm), and solid solution alloying additions of zirconium on the cleavage fracture stress (σF) of polycrystalline niobium. Extensive fracture surface analyses of fractured notched-bend specimens revealed the location of the apparent cleavage fracture nucleation sites, while comparisons have been made to peak stress locations using existing finite element models. The effects of such microstructural changes on the magnitude of the cleavage fracture stress are rationalized via comparisons to models for cleavage fracture.

Dislocation structures in zirconium and zircaloy-4 fatigued at different temperatures

Abstract: The development of characteristic dislocation structures in pure zirconium and zircaloy-4 fatigued under pull-push strain control as the testing temperature and the cyclic strain range varied was examined using a thin-foil transmission electron microscopy (TEM) technique. The slip planes and the twinning planes were determined by a standard stereographic trace analysis technique. The first-order prismatic slip {10\(\bar 1\)0} is the primary deformation mode in zirconium and zircaloy-4 fatigued from room temperature (RT) to 873 K. The pyramidal sli {\(\bar 1\)2\(\overline {11} \)} is activated at 673 K and at high cyclic strain ranges, whereas the basal slip {0001} only appears in those specimens fatigued at 873 K. The {10\(\bar 1\)2}, {11\(\bar 2\)1}, and {11\(\bar 2\)2} types of twins were detected in specimens fatigued at RT. Twinning becomes less frequent as the testing temperature increases. The schematic map of the cyclic deformation modes as a function of the plastic strain range and the test temperature is described. The dislocation configurations in fatigued pure zirconium specimens evolve from a planar arrangement to a cell structure as the test temperature and the strain range increase. For zircaloy-4, the fatigued dislocation structure is parallel dislocation lines at RT, cells at 673 K, and two sets of approximate mutually perpendicular dislocation bands at 873 K, respectively. Finally, the fatigued dislocation-structure evolution map with the cyclic strain range and the test temperature are qualitatively established for zirconium and zircaloy-4, respectively. The effect factors on the fatigue mechanism and the thermodynamic and dynamic criteria of the dislocation-pattern evolution are discussed.

Use of Portable/ in situ Stress-Strain Microprobe System to Measure Stress-Strain Behavior and Damage in Metallic Materials and Structures

Abstract: A novel portable/in situ Stress-Strain Microprobe (SSM) system was used to measure true-stress/true-plastic-strain ({sigma}{sub t}-{epsilon}{sub p}) behavior of several metallic materials, welds, and their heat-affected-zones (HAZs) in various metallurgical and damage conditions. The SSM system utilized an automated ball indentation (ABI) technique to measure elastic modulus, yield strength, {sigma}{sub t}-{epsilon}{sub p} curve, strength coefficient, strain-hardening-exponent (uniform ductility), and to estimate fracture toughness (from the ABI-measured flow properties) in carbon steels, stainless steels, nickel alloys, aluminum alloys, titanium alloys, zirconium alloys, etc. Numerous ABI tests were also conducted on several nuclear pressure vessel steels (NPVSs) in the unirradiated, neutron irradiated, and post-irradiated thermally-annealed conditions. For all these test materials and conditions, the ABI-derived results were in good agreement with those from conventional standard test methods. Furthermore, the nondestructive ABI test results rigorously indicated the various levels of neutron-embrittlement damage and the percentage of ductility recovery following thermal annealing of the NPVS specimens. In situ/nondestructive structural applications of the SSM system and its ABI technique have been demonstrated by testing a circumferentially welded stainless steel pipe and a full-thickness section of a nuclear pressure vessel (using 90{degrees}V-blocks and magnetic mounts for temporary attachment of the SSM testing head to the pipe andmore » the steel section, respectively). All SSM localized tests were computer-controlled and conducted in less than 2 minutes per ABI test; depending on the desired strain rate. Example test results on metallic structural components and samples are presented in this paper. 21 refs., 5 figs., 1 tab.« less

Residual stresses in steel and zirconium weldments

Abstract: Three-dimensional scans of residual stress within intact weldments provide insight into the consequences of various welding techniques and stress-relieving procedures. The neutron diffraction method for nondestructive evaluation of residual stresses has been applied to a circumferential weld in a ferritic steel pipe of outer diameter 114 mm and thickness 8.6 mm. The maximum tensile stresses, 250 MPa in the hoop direction, are found at mid-thickness of the fusion zone. The residual stresses approach zero within 20 mm from the weld center. The residual stresses caused by welding zirconium alloy components are partially to blame for failures due to delayed-hydride cracking. Neutron diffraction measurements in a GTA-welded Zr-2.5 Nb plate have shown that heat treatment at 530 C for 1 h reduces the longitudinal residual strain by 60%. Neutron diffraction has also been used to scan the residual stresses near circumferential electron beam welds in irradiated and unirradiated Zr-2.5 Nb pressure tubes. The residual stresses due to electron beam welding appear to be lower than 130 MPa, even in the as-welded state. No significant changes occur in the residual stress pattern of the electron-beam welded tube, during a prolonged exposure to thermal neutrons and the temperatures typical of an operating nuclearmore » reactor.« less

The characteristics of surface oxidation and corrosion resistance of nitrogen implanted zircaloy-4

Abstract: This work is concerned with the development and application of ion implantation techniques for improving the corrosion resistance of zircaloy-4 The corrosion resistance in nitrogen implanted zircaloy-4 under a 120 keV nitrogen ion beam at an ion dose of 3 × 1017 cm−2 depends on the implantation temperature The characteristics of surface oxidation and corrosion resistance were analyzed with the change of implantation temperature It is shown that as implantation temperature rises from 100 to 724°C, the colour of specimen surface changes from its original colour to light yellow at 100°C, golden at 175°C, pink at 300°C, blue at 440°C and dark blue at 550°C As the implantation temperature goes above 640°C, the colour of surface changes to light black, and the surface becomes a little rough The corrosion resistance of ziracaloy-4 implanted with nitrogen is sensitive to the implantation temperature The pitting potential of specimens increases from 176 to 900 mV (SCE) as the implantation temperature increases from 100 to 300°C, and decreases from 900 to 90 mV(SCE) as the implantation temperature increases from 300 to 640°C The microstructure, the distribution of oxygen, nitrogen and carbon elements, the oxide grain size and the feature of the precipitation in the implanted surface were investigated by optical microscope, TEM, EDS, XRD and AES The experimental results reveal that the ZrO2 is distributed mainly on the outer surface The ZrN is distributed under the ZrO2 layer The characteristics of the distribution of ZrO2 and ZrN in the nitrogen-implanted zircaloy-4 is influenced by the implantation temperature of the sample, and in turn the corrosion resistance is influenced

Electrical and structural properties of zirconium germanosilicide formed by a bilayer solid state reaction of zr with strained si1-xgex alloys

Abstract: The effects of alloy composition on the electrical and structural properties of zirconium germanosilicide (Zr–Si–Ge) films formed during the Zr/Si1−xGex solid state reaction were investigated. Thin films of Zr(Si1−yGey) and C49 Zr(Si1−yGey)2 were formed from the solid phase reaction of Zr and Si1−xGex bilayer structures. The thicknesses of the Zr and Si1−xGex layers were 100 and 500 A, respectively. It was observed that Zr reacts uniformly with the Si1−xGex alloy and that C49 Zr(Si1−yGey)2 with y=x is the final phase of the Zr/Si1−xGex solid phase reaction for all compositions examined. The sheet resistance of the Zr(Si1−yGey)2 thin films was higher than the sheet resistance of similarly prepared ZrSi2 films. The stability of Zr(Si1−yGey)2 in contact with Si1−xGex was investigated and compared to the stability of Ti(Si1−yGey)2 in contact with Si1−xGex. The Ti(Si1−yGey)2/Si1−xGex structure is unstable when annealed for 10 min at 700 °C, with Ge segregating from Ti(Si1−yGey)2 and forming Ge-rich Si1−zGez pr...

Low-melting-point titanium-base brazing alloys. Part 1: Characteristics of two-, three-, and four-component filler metals

Abstract: The melting point, microstructure, phase, and electrochemical behavior of Ti-21Ni-15Cu alloy, together with two-, three-, and four-component low-melting-point titanium-base brazing alloys, are presented in this paper Five filler metals were selected for the study, in which melting points were measured by differential thermal analysis, phases identified by x-ray diffractometry, and corrosion behaviors tested by potentiodynamic polarization The experimental results show that the three-component Ti-15Cu-15Ni and the newly developed Ti-21Ni-14Cu alloys exhibit the combination of lower melting point and superior corrosion resistance compared to the two-and four-component titanium alloys, 316L stainless steel, and a Co-Cr-Mo alloy in Hank’s solution at 37 °C On a short time basis, the presence of Ti2Ni and Ti2Cu intermetallics in the Ti-15Cu-15Ni and Ti-21Ni-14Cu alloys should not be preferentially dissolved in galvanic corrosion with respect to the dissimilar Ti-6Al-4V alloy

Pitting Corrosion of Amorphous Ni–Zr Alloys in Chloride Ion Containing Sulfuric Acid Solutions

Abstract: The pitting corrosion behavior of the melt-spun amorphous Ni-Zr alloys with 30-75 at% zirconium, the crystalline arc-melted counterparts and the sputter-deposited Ni-Zr alloys with 20-84 at% zirconium was examined by electrochemical measurements in deaerated 0.5 kmol/ m 3 H 2 SO 4 with and without 0.1 kmol/m 3 NaCl at 303 K. In the sulfuric acid solution without Cl - , these alloys were spontaneously passive and their potentiodynamic behavior was similar to each other. In the Cl - -containing solution, all the melt-spun amorphous alloys suffered pitting during anodic polarization and the pitting potential decreased with an increase in zirconium content. On the other hand, the crystalline arc-melted low zirconium alloys suffered pitting but no pitting observed for the crystalline alloys containing 70 at% zirconium or more. In addition, the pitting potential increased with the zirconium content of crystalline alloys. All the sputter-deposited alloys did not suffer pitting regardless of the amorphous and crystalline structures. Therefore, the melt-spun amorphous alloys were the most susceptible to pitting corrosion. A marked difference was observed in the pitting behavior between the shiny side (top side) and the dull side (wheel side) surfaces of the melt-spun ribbon. The pits initiated from the dull side surface. Thus, the dull side surface could be responsible for such an unusual pitting behavior of the melt spun ribbon.

Fuel rod for light water reactor and method for manufacturing the same

Abstract: A fuel rod for a light water reactor comprises a cladding tube which comprises a zirconium alloy having a composition including 0.6 to 2.0% by weight of Nb, 0.5 to 1.5% by weight of Sn, 0.05 to 0.3% by weight of Fe, and the balance being Zr and incidental impurities; uranium oxide fuel pellets packed in the cladding tube; and end plugs closing both ends of the cladding tube. The cladding tube is sealed by TIG welding with the end plugs. Precipitates having grain diameters of 0.01 to 0.5 μm and comprise intermetallic compounds containing Zr, Nb and Fe are present at grain boundaries in the structure of heat affected zones of the cladding tube, the heat affected zone being adjacent to a bead formed by TIG welding.

Zirconium-based alloy, manufacturing process, and use in a nuclear reactor

Abstract: The alloy has a base composition similar to that of a zirconium alloy of known type used for the manufacture of an element intended for use in the core of a nuclear reactor, such as a cladding tube, a guide tube, or another structural element of a fuel assembly. In addition, the alloy contains sulphur in a proportion by weight of between 8 and 100 ppm and preferably between 8 and 30 ppm.

Auger electron spectroscopy study of oxidation behavior of iron and chromium in Zr(Fe,Cr)2 precipitate in zircaloy-4

Abstract: The oxidation behavior of Zr(Fe,Cr)2 precipitates being present at the surface of Zircaloy-4 was examined with microprobe Auger electron analysis, focussing attention on the oxidation behavior of chromium and iron in the early stage of oxidation where the oxide film was coherent. Chromium formed a thin oxide layer at the top surface of the zirconium oxide film of precipitate and remained in a metallic state inside the oxide film. Iron was oxidized via dissolution in the matrix zirconium oxide near the top surface and remained in a metallic state inside the oxide film. Such variety of chemical state of chromium and iron with depth in the oxide film was attributed to the existence of oxygen potential gradient in the oxide film.