Creation of ternary Ni-Cr-W alloys with a sharp cube texture and a curie temperature below 77 K to produce epitaxial substrates for superconducting compositions

The texture, structure, and magnetic and mechanical properties of thin tape substrates fabricated of nickel alloys with chromium and tungsten have been investigated. It has been shown that in Ni_89.6Cr_8.6W_1.8 and Ni_89.6Cr_7.8W_2.6 alloys a sharp cube texture can be formed, which is stable up to high annealing temperatures. In the Ni_89.2Cr_7.2W_3.6 alloy, other orientations are present along with a cube component. The possibility of obtaining a sharp cube texture after primary recrystallization is connected with the quantitative relationship between the texture components in a cold-rolled tape, which is determined by the method of orientation-distribution functions. The alloys studied are paramagnetic at 77 K.     

Textured tape substrates from binary copper alloys with vanadium and yttrium for the epitaxial deposition of buffer and superconducting layers

The structure of tapes of binary Cu–0.6 wt % V and Cu–1 wt % Y alloys and texturing process of them in the course of cold deformation by rolling to ~99% and subsequent recrystallizing annealing have been studied. The possibility of achieving the perfect cube texture in thin tapes made from binary copper-based alloys with vanadium and yttrium additions has in principle been shown. This opens the prospect of using them as substrates when manufacturing tapes of second-generation high-temperature superconductors. Optimum annealing conditions for the studied alloys have been determined, which have made it possible to produce the perfect biaxial texture with a content of cube {001}〈100〉 ± 10° grains on the surfaces of textured tapes of more than 95%.     

Formation of segregation inhomogeneity in high-temperature nickel-base alloys

The process of hardening of model high-temperature nickel alloys with additives of Nb, Mo, Ti, W is studied in a range of cooling rates typical for large castings. The rules of the segregation processes and the formation of the structure are described. It is shown that despite the low volume fraction of the eutectic component its morphology and laws of formation have a considerable effect on the structural homogeneity of the alloy. Carbide, intermetallic, and carbide-intermetallic eutectics can form in the alloys depending on the cooling conditions. The diffusion processes in crystallization of the alloys are a sign of active mass exchange between the eutectic liquid and the primary solid phases. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 19–22, February, 1999.     

Formation of recrystallization cube texture in high purity face-centered cubic metal sheets

An investigation on recrystallization textures in high purity face-centered cubic (fcc) aluminum, copper, and nickel indicated that the cube texture is a unique dominant final texture. In a macroview of rolling deformation, a balanced activation of four slip systems can result in certain stability of some substructure with cube orientation in the deformed matrix. In the stable substructure the dislocation density is very low, and the dislocation configuration is rather simple in comparison to other orientations so that the cube substructure can easily be transformed into cube recrystallization nuclei by a recovery process. A high orientation gradient and correspondingly high angle boundaries to the deformed matrix are usually expected around the cube nuclei, which, therefore, grow rapidly. After the primary recrystallization, the size of cube grains is much larger than the grains with other orientations, which will be expensed as the cube grains grow further, so that the cube texture can finally become a dominant texture component.     

Growth texture due to directed crystallization of high-temperature nickel alloys

Processes of formation of growth texture [001] due to directed crystallization of high-temperature nickel alloys are considered and their qualitative and quantitative characteristics determined. Simulation of competitive growth is performed for flat bicrystal ingots. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 25–32, August, 2006.     

Formation of cube texture during annealing of rolled tapes from alloys Ni95.3Mo4.7 and Ni48.8Fe51.2

The paper deals with the study of the process of the formation of the primary recrystallization texture in Ni_95.3Mo_4.7 and Ni_48.8Fe_51.2 nickel alloys during annealing after deformation by rolling to large reduction. The electron backscatter diffraction method is used to show the effect of the temperature and the heating rate during annealing on the structure and texture in alloys that differ in the temperature of the beginning of primary recristallization. The majority of attention is focused on investigating the possibility of estimating the temperature range of primary recrystallization from the dilatometry anomaly on the temperature dependence of the thermal expansion coefficient. Variations in the relief of the rolled tapes after recrystallization are studied.     

Effect of recrystallization annealing on the formation of a perfect cube texture in FCC nickel alloys

Based on the data of X-ray diffraction, dilatometry, transmission electron microscopy, and electron backscatter diffraction, the optimum regimes of heat treatment of cold-rolled (to 98.5–99%) tapes made of binary Ni-W, Ni-Cr, Ni-Fe and ternary tungsten-containing Ni-Pd-W and Ni-Cr-W alloys that are widely utilized in the world practice for the fabrication of high-temperature superconducting cables of the second generation, which make it possible to obtain a perfect cube texture. In all five alloys, the spreed of the texture upon slow heating and two-step annealing decreases by 0.2°–1.5° around the RD and by 0.1°–0.6° around the RD in comparison with the single-stage high-temperature annealing.     

Using high-temperature superconductors for levitation applications

Melt-textured, bulk high-temperature superconductors are finding increasing uses in superconducting bearings, flywheel energy storage, and other levitational applications. This article reviews the use of these materials in magnetic-levitation applications. The behavior of levitational force, stiffness, damping, and rotational losses is discussed. For more information, contact J.R. Hull, Argonne National Laboratory, ET-335, Argonne, Illinois 60439; (630) 252-8580; fax (630) 252-5568; e-mail jhull@anl.gov.     

Reviewing some current theories for high-temperature superconductors

In this article, some theories on the properties of high-critical-temperature superconductors are briefly reviewed, with a special emphasis on those theories based on pairing by antiferromagnetic fluctuations and the resonating-valence-bond scenarios. Ideas linking the physics of the cuprates with those of the recently discovered ladder materials are presented. Possible explanations for the spin gap in the high-critical-temperature materials using preformed pairs and stripes are briefly discussed. The goal of this article is to provide simple explanations for the main ideas and concepts, while keeping the mathematical and computational details to a minimum. E. Dagotto earned his Ph.D. in physics at the Instituto Balseiro, Argentina, in 1985. He is currently a professor in the Department of Physics and National High Magnetic Field Laboratory at Florida State University.     

Trends in high-temperature alloys

A review of developments in superalloys and chromium-base alloys, including the needs and trends seen to the year 1970.     

Influences of cube texture on etched foil capacitance

The influences of aluminum cube texture on etched foil qualities and current efficiency were studied in this paper. The present results indicated that the decrease of cube texture (volume fraction) would lead to the decrease of tunnel densities on etched foils. Current efficiency changed little with cube texture and could reach up to 98%. The same current efficiency led to the same electrochemical corrosion weight loss, which caused the etched foils with a smaller tunnel density had a larger tunnel size. The same electrochemical corrosion weight loss would also lead to the etched foils produced by different cube texture foil have the same folding endurance. The etched foil produced by the foil with a better cube texture would have a larger tunnel density, which caused the capacitance of it was larger.     

NiAl alloys for high-temperature structural applications

If their properties can be improved, nickel aluminide alloys offer significant payoffs in gas turbine engine applications. For these materials, excellent progress has been made toward understanding their mechanical behavior as well as improving their low-temperature ductility and high-temperature strength. For example, recent work shows that room-temperature ductility can be improved dramatically by microalloying with iron, gallium or molybdenum. The next challenge is to develop an alloy which has the required balance of ductility, toughness and strength. Development of design and test methodologies for components made out of low-ductility, anisotropic materials will also be required. While significant challenges remain, the continuing developments suggest that the prognosis for using NiAl alloys as high-temperature structural materials is good.     

Formation of texture in thin tapes of Fe-Ni alloys during cold rolling and recrystallization

A quantitative analysis of rolling textures in iron-nickel alloys with a wide range of concentrations of the alloying element has been performed by analyzing the orientation distribution function. It has been found that, despite a considerable increase in the lattice parameter of the alloys under study, their deformation texture is similar to the deformation texture of pure nickel, making it possible to produce a perfect cube texture after primary recrystallization. It has been shown that the use of two-step annealing allows improving the sharpness of the cube texture in the iron-nickel alloys studied.     

Formation of aluminide coatings on Fe-based alloys by chemical vapor deposition

Aluminide and Al-containing coatings were synthesized on commercial ferritic (P91) and austenitic (304L) alloys via a laboratory chemical vapor deposition (CVD) procedure for rigorous control over coating composition, purity and microstructure. The effect of the CVD aluminizing parameters such as temperature, Al activity, and post-aluminizing anneal on coating growth was investigated. Two procedures involving different Al activities were employed with and without including Cr–Al pellets in the CVD reactor to produce coatings with suitable thickness and composition for coating performance evaluation. The phase constitution of the as-synthesized coatings was assessed with the aid of a combination of X-ray diffraction, electron probe microanalysis, and existing phase diagrams. The mechanisms of formation of these CVD coatings on the Fe-based alloys are discussed, and compared with nickel aluminide coatings on Ni-base superalloys. In addition, Cr–Al pellets were replaced with Fe–Al metals in some aluminizing process runs and similar coatings were achieved.     

Processes leading to formation of cube texture in cold-rolled Ni-Cr-W alloy

Behavior of cold-rolled fcc Ni_88.4Cr_9.2W_2.4 alloy during heating has been studied. Two consecutive exothermic processes were detected using differential scanning calorimetry, high-temperature X-ray diffraction, and dilatometry. The processes were identified as polygonization and recrystallization, which lead to cube texture formation, as was shown by X-ray diffraction and electron backscatter diffraction. The heat effects of these processes were determined.