Strong Cube Texture Research Articles

Texture Control in Non-Oriented Electrical Steels by Severe Plastic Deformation

Although plenty of research has already been carried out on the issue of texture control in non-oriented electrical steels, there is not yet a universally applied industrial process to obtain an optimized {001} fibre texture. Among the various laboratory processes that have been studied so far, cross rolling seems to be one of the most promising approaches. For evident reasons cross-rolling cannot be implemented on a conventional continuous rolling line of an industrial plant. In the present study a potential interesting alternative is presented which may deliver a similar texture evolution as the cross rolling process, but can be applied in a continuous line of hot and cold rolling operations followed by recrystallization annealing. By applying severe rolling reductions a very strong rotated cube texture is obtained very much similar to the one that is observed after cross rolling. After annealing, the rotated cube texture changes to a {h11}<1/h,21> fibre texture with a maximum on the {311}<136> component which implies the potential to develop a {001} fibre texture after further processing. It is argued that the appearance of the {311}<136> recrystallization texture component can be attributed to oriented nucleation in the vicinity of grain boundaries between slightly misoriented rotated cube grains.

Application of textured IBAD-TiN buffer layers in coated conductor architectures

Ion-beam assisted deposition (IBAD) is one of the major techniques for preparing highly textured templatesfor YBa2Cu3O7−x (YBCO) coated conductors. In most applications so far IBAD-MgO has beenused. TiN is an alternative material for the IBAD process showing a texturednucleation similar to MgO. Different amorphous or nanocrystalline seed layers such asAl2O3,Y2O3 orTa0.75Ni0.25 were found to be suitable for achieving strong cube textures in film thicknessesbelow 10 nm using reactive ion-beam assisted pulsed laser deposition. The biaxialtexture was preserved to a higher thickness using homoepitaxial growth athigher temperatures. Different buffer layer architectures based on IBAD-TiNhave been developed on Hastelloy substrates. An electrically conducting bufferlayer stack was realized using a double layer of Au and Ir with a final Nb-dopedSrTiO3 cap layer, enabling the epitaxial growth of YBCO on top.Alternatively, a robust simplified buffer architecture was studied usingSrZrO3 directly on TiN, leading to highly textured YBCO layers.

Evolution of Rolling Textures of Cold Rolled Copper Foils

The texture evolution of cold rolled tough pitch copper foils could be changed by altering the initial texture and microstructure before cold rolling. The development of β-fiber texture was substantially suppressed even after 92% reduction for the case of abnormally coarse initial grain structure and extremely strong initial cube texture. Instead, the intensity of cube and RD (rolling direction)-rotated cube texture components was increased continuously by increasing the intensity of the initial cube texture.

Influence of impurity hydrogen on coarse grain evolution in high purity aluminum foils for electrolytic capacitors

Two aluminum plates with 99.99 mass% purity with different hydrogen contents of 0.17 and 0.41 mass ppm were hot-rolled to 10 mm in thickness, cold-rolled by 99% to 130 μm in thickness, annealed at 250°C for 2 h, cold-rolled by 15% to 110 μm in thickness and finally annealed, which is similar to commercial processes of high purity aluminum foils for electrolytic capacitors. The foils were subjected to optical macro- and micro-scopies, thermal desorption spectroscopy (TDS), hydrogen micro-print technique (HMPT) and electron back-scattering diffraction pattern (EBSP) analysis and the effect of impurity hydrogen on the growth of off-cube grains in a recrystallized microstructure with a strong cube texture was investigated. It was confirmed that abnormal grain growth of off-cube grains becomes more conspicuous with the increase in the amount of impurity hydrogen in the original ingot. The HMPT analysis showed that hydrogen concentration in the cube-oriented region was larger than in the off-cube grain. The grain size in the cube-oriented region decreased with decreasing hydrogen content. From these facts and the result of TDS, supersaturated hydrogen atoms were presumed to segregate to low angle grain boundaries, the boundaries between cube-oriented grains, which can provide the driving force for the abnormal grain growth.

Ion-beam assisted pulsed laser deposition of textured transition-metal nitride films

AbstractIon-beam assisted deposition (IBAD) offers the possibility to prepare thin textured films on amorphous or non-textured substrates. It was shown within the last decade that the ion beam influences the nucleation in material with a rocksalt structure leading to a strong cube texture already within the first 10 nanometres. Among these materials, transition metal nitrides exhibit interesting physical properties as superconductivity, metallic behaviour or superior hardness. Therefore, a reactive IBAD process was applied for the preparation of highly textured transition metal nitride layers using pulsed laser deposition of pure metals in combination with a nitrogen-containing ion beam. The results on the in-plane textured growth of TiN are promising for the development of conducting buffer layer architectures for YBCO coated conductors based on the IBAD approach. Furthermore, this approach was used to prepare other highly textured transition metal nitride thin films like NbN and ZrN.

Anomalous Rolling and Annealing Textures of Cold Rolled Copper Foils

Copper foils cold rolled up to 92% reduction exhibited a low intensity of the β-fiber texture and a high intensity of the cube and RD (rolling direction)-rotated cube components. After annealing, the recrystallization texture of the foils could be characterized by the mixture of the cube and the S components. An initial strong cube texture with a large grain size might remain a less developed rolling texture component, cube or RD-rotated cube, which would be the source of the S component in the recrystallization texture.

Influence of texture and grain structure on strain localisation and formability for AlMgSi alloys

Abstract The influence of texture and grain structure on strain localisation and formability is examined by experiments and numerical simulations for the extruded aluminium alloys AA6063 and AA6082. In the as-extruded condition, the AA6063 alloy has an equiaxed, recrystallised grain structure with strong cube texture, while AA6082 has a fibrous, non-recrystallised grain structure with strong β-fibre texture. By deforming and heat treating the materials after extrusion, a recrystallised equiaxed grain structure with a close to random texture is obtained for both alloys. A comprehensive test programme is conducted to determine the work hardening, plastic anisotropy and formability of the materials. Strain localisation and failure are examined by optical microscopy. An anisotropic plasticity model is calibrated for the materials and used in calculation of forming limit curves by means of the Marciniak–Kuczynski (M–K) analysis for anisotropic materials. It is found that strong cube texture leads to superior formability properties for biaxial stretching while random texture slightly lowers the formability. The strong β-fibre texture of AA6082 in the as-extruded condition leads to reduced formability. The results of the M–K analysis are very conservative compared with the experimental results, and a parametric study is undertaken to investigate the sensitivity of the predicted forming limit curves to some parameters not well defined by the experiments.

An experimental and numerical study on the formability of textured AlZnMg alloys

Abstract The influence of texture and grain structure on strain localisation and formability is investigated experimentally and numerically for two AlZnMg alloys. The considered alloys have recrystallised or non-recrystallised grain structure and strong or nearly random texture. The textured materials have rotated cube texture or β-fibre texture of high intensity. A comprehensive test programme, including uniaxial tension tests in three directions, through-thickness compression tests, plane-strain tension tests and double-plate formability tests, is completed to determine the work hardening, plastic anisotropy and formability of the materials. Strain localisation and failure are examined by optical microscopy. Using parts of the test data, an anisotropic plasticity model is calibrated and applied in calculation of forming limit curves, using the Marciniak–Kuczynski (M-K) analysis for anisotropic materials. The formability tests show that the materials with nearly random texture exhibit superior formability. This is mainly attributed to enhanced work hardening for these materials. For the material exhibiting strong β-fibre texture significantly lower formability is found in equibiaxial stretching than in plane strain, while this characteristic is not seen for the material with strong cube texture. The M-K analysis is capable of predicting the major trends of the experiments, and captures the low formability of the alloy with strong β-fibre texture under equibiaxial straining. A numerical study is performed to evaluate the sensitivity of the predicted forming limit curves to parameters not determined experimentally.

Development of cube textured Ni–5at.%W alloy substrates for YBCO coated conductor application using a powder metallurgy process

In this paper, Ni–5at.%W alloy substrate for YBCO coated conductor was fabricated by a dry powder metallurgy process including powder compaction, cold isostatic pressing (CIP), cold rolling and annealing for recrystallization. Ni and W powders were ball-milled at this process for various times of 10, 30, 50 and 100h in argon atmosphere. The rod-like Ni–W alloy compacts were sintered at 1150°C for 1h in 96%Ar–4%H2 atmosphere. The sintered rods were cold rolling into thin tape of 70–90μm thickness with 5% reduction at each path. The Ni–W alloy tapes were annealed at 800–1200°C in an atmosphere of 96%Ar–4%H2 mixing gas for the development of cube texture. The tape with the best properties of low surface roughness, small grain size and strong cube texture was obtained at the condition annealed at 1200°C using ball-milled powder for 30min. The W addition to Ni improved the mechanical properties by solid solution hardening and inhibited grain growth for annealing heat treatment. The tapes were characterized by X-ray pole-figure, optical microscopy (OM), scanning electron microscopy (SEM) and scanning probe microscopy (SPM).

Crystallographic Orientation Distribution Control by Means of Continuous Cyclic Bending in a Pure Aluminum Sheet

Continuous cyclic bending (CCB) has been proposed as a useful straining technique to produce the high strain on the surface layers and the lower strain in the central layer of the sheet. A pure aluminum sheet is worked by the CCB using the Roll traveling and Roll driven machine. It is found that a sharp Cube orientation is formed by the CCB and subsequent annealing in the pure aluminum sheet. Influences of the CCB/annealing process parameters such as partial or final annealing temperature, strain inside grains and repeating effect, on the Cube sharpening are investigated. The sharper Cube orientation is obtained for the higher temperature of the final annealing after the roll traveling device CCB. While a considerably strong Cube texture appears after one routine of the roll driven machine CCB/773 K-3.6 ks, the texture is weakened after two routines repeated to change into a random texture. The 10 Pass and 20 Pass CCBs with a comparatively low degree of working before partial annealing lead to a high Cube fraction more than 60%.

Texture Evolution in Ni Substrate Prepared by Powder Metallurgy and Casting Methods

Cube textured Ni substrate were fabricated for YBCO coated conductors from the initial specimens prepared by powder metallurgy (P/M) and casting and the effects of annealing temperature and reduction ratio on texture formation and microstructural evolutio were evaluated. The initial specimens were rolled by 98.6% and 99.2% reduction ratio and then annealed in the temperature range of 600°C to 1200°C. The microstructure and texture were evaluated by optical microscopy and X-ray pole-figure analysis. We observed that microstructure of the initial specimen varied with preparation methods.Texture analysis indicated that a strong cube texture formed for substrate made by P/M, and the degree of texture did not significantly vary with annealing temperature of 600°C~1100°C. On the other hand, the texture of substrate made by casting was more dependent on the annealing temperature and twin texture ({221}<221>) and several minor texture components started to form at 1000°C. In addition, the texture of substrate made by P/M was significantly dependent on the reduction ratio.

Detailed investigations on La 2Zr 2O 7 buffer layers for YBCO-coated conductors prepared by chemical solution deposition

An extensive study of the growth and properties of La 2Zr 2O 7 (LZO) buffer layers prepared by chemical solution deposition on Ni–5 at.%W rolling-assisted biaxially textured substrates, which is presently of great interest for the preparation of YBa 2Cu 3O 7− x -coated conductors, is presented. The main focus was on the understanding of the decomposition of the precursor layers, and their growth and texture formation, as well as their structural evolution during annealing, leading to highly biaxially textured LZO buffer layers. Therefore, various characterization methods, including spectroscopic analysis techniques, X-ray diffraction techniques, and other techniques, were applied. Epitaxially grown LZO buffer layers of high performance, showing a strong cube texture up to the surface, a crack-free surface morphology of low roughness, and a sufficient barrier function against Ni diffusion from the substrate, were reproducibly obtained.

A novel technique for developing composite substrates used in YBCO coated conductors

We report on a novel technique of sparking plasma sintering to prepare Ni–W alloy composite substrates with strong cube texture, high yield strength and reduced magnetization for coated conductors. It was found that an outer Ni–5 at.% W layer in as-obtained composite substrates has a sharp and pure cube texture, while the use of the Ni alloy with high W content in the core of the composite substrates not only enhances the mechanical property, but also degrades the ferromagnetism of the whole substrates.

The Influence of Grain Structure and Texture on Formability and Toughness of Extruded Aluminium Alloys

The main focus in this work is to investigate the effect of crystallographic texture, grain structure and dispersoids on formability and toughness in some industrial 6xxx and 7xxx series alloys. Materials of these alloys showing strong cube textures or β-fibre deformation textures in as extruded condition have been compared with the same alloys processed by rolling and heat treatment to obtain a random texture. It is found that the formability depends on the temper and the texture and that the effect of the latter is path dependent. Materials with a random texture have a significant higher formability in terms of uniform elongation than materials with cube texture when deformed in the W-temper condition. Forming in other deformation modes shows less difference between the cube and random texture. However, a fibrous grain structure with a sharp β-fibre texture shows an anomalous behaviour when deformed in the biaxial deformation regime. Toughness, in terms of Charpy energy and local strains in the necking area, is significantly higher for materials with a cube texture as compared to materials with random textures. This difference is explained by variations in the dispersoid levels, grain structures (size and grain boundary misorientation) and the texture.

Development of textured Ni substrates prepared by powder metallurgy and casting

We fabricated the textured Ni substrate for YBCO coated conductors and evaluated the effects of processing variables on microstructural evolution and texture transformation. Initial specimens were prepared by two different methods, i.e., powder metallurgy (P/M) and casting. To characterize the role of two preparation methods, the initial specimens of the same size were prepared under the same rolling and annealing conditions. The microstructure and texture were evaluated by orientation distribution function (ODF), electron backscattering diffraction and transmission electron microscopy with selected area diffraction. We observed that the microstructure of the rolled tape varied with preparation methods; the rolled tape prepared by P/M had more deformation bands and stronger β-fiber texture than that one obtained by casting, resulting in finer microstructure and stronger cube texture after recrystallization. The smaller grains in the former tape were explained by the “variation inhibition theory” together with in situ TEM result. Texture analysis indicated that the substrate made by P/M had a stronger cube texture and a wider annealing temperature range in which the cube texture became stable, compared to that of the casting-substrate. In addition, abnormal grain growth occurred and consequently formed high angle grain boundary for substrate by casting but not for substrate by P/M.

Origins of Cube Recrystallization Textures in Heavily Rolled High Purity Al

In high purity (4N) Al containing 50 ppm Cu, very strong cube textures can be developed by cold rolling 98 % and annealing at 500 °C. The orientation density in this material amounted to as much as 220 times random, i. e. about 3 times stronger than that observed in standard 4N Al. It is expected that the origins of cube textures should be most unambiguously clarified by using this material. Commercial hot bands of this materials were cold rolled 98 % to the thickness of 132 μm and isothermally annealed at 230 °C. Detailed EBSP analyses were made both on the rolling plane and on the longitudinal section at each stage of annealing. It was found that in the hot band of this high purity Al, cube orientations were mostly rotated away into other orientations due to low temperature hot rolling with high rolling reductions. Therefore, regions having cube orientations were very few. They were not present in the form of so called cube bands, which had been reported in previous investigations, but in the form of isolated, rather equi-axed recrystallized grains. After 98 % cold rolling, these remaining cube regions were fragmented, and further rotated away into other orientations, so that only very few cube oriented regions were observed in the cold rolled materials. However, it was from such deformed cube oriented regions that the most potential exact cube recrystallized grains were formed. They were nucleated much earlier and grew much faster than grains of other orientations.

YBCO Coated Conductor Applications - A Texture Problem

YBa2Cu3O7-δ ("YBCO") is a high-temperature ceramic superconductor. Due to its complex layered structure, a strong biaxial texture of the YBCO grains is necessary to achieve technically relevant currents. In this paper, we describe the development of flexible metallic tapes with strong cube texture, providing a lattice-matched template for buffer and YBCO coatings in proper orientation. Texture analysis was performed using electron backscatter diffraction (EBSD).

Comparison of the texture evolution of direct chill and continuous cast AA5052 hot bands during isothermal annealing

As-received commercial direct chill cast (DC) and continous cast (CC) AA5052 hot bands were isothermally annealed at different temperatures. The variations of electrical resistivity, hardness, microstructure, and texture of these hot bands during annealing were examined. Texture was investigated by X-ray diffraction. The variation in texture volume fractions with annealing time was quantitatively analyzed by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. The orientation maps of the partially and fully recrystallized samples were characterized by electron backscattered diffraction (EBSD). It was found that electrical resistivity of the CC AA5052 hot band was higher than that of the DC AA5052 hot band. The electrical resistivity of CC AA5052 decreased more significantly than that of DC AA5052 during isothermal annealing. The DC AA5052 hot band was more easily recrystallized than CC AA5052 hot band during annealing. After complete recrystallization, DC AA5052 hot band possessed a stronger cube texture than the CC AA5052 hot band. The texture evolutions of DC and CC AA5052 can be expressed quantitatively by the JMAK equation after the volume fractions of the texture components are calculated by an improved integration method. Annealing temperature had an influence on the n values in the JMAK-type equations. The n values are small at low annealing temperatures.

Investigation of Processing Variables of Ni Substrate for YBCO Coated Conductors

We fabricated cube textured Ni substrates for YBCO coated conductors from the initial specimens prepared by powder metallurgy (P/M) and casting and evaluated the effects of annealing temperature on microstructural evolution and texture formation. To characterize the roles of the two preparation methods, the initial specimens were prepared to be of the same size and experienced the same rolling conditions, and were then annealed in the temperature range of 600/spl deg/C to 1200/spl deg/C. The texture was evaluated by X-ray pole-figure analysis and transmission electron microscopy (TEM). The texture analysis indicated that a strong cube texture formed for the substrate made by P/M and this texture did not vary significantly with annealing temperature in the range of 600-1200/spl deg/C. On the other hand, the texture of the substrate made by casting was more dependent on the annealing temperature, and a twin texture ({221} ) and several minor texture components began to form at 1000/spl deg/C. Microstructural observation showed that the morphology of deformation band together with micro-band in the as-rolled tape prepared by P/M was more homogeneous and of higher density than that produced by casting, resulting in a strong cube texture in wider range of annealing temperatures and a finer microstructure after recrystallization.

Effect of W Addition on the Microstructure and Properties of Ni-W Substrates for Coated Conductors

We fabricated Ni and Ni-W alloys for use as substrates in YBCO coated conductor applications and evaluated the effects of the W addition on the texture, microstructure, and mechanical and magnetic properties of the substrate. Pure Ni and Ni-W (2, 3, and 5 at.%) alloys were prepared by plasma arc melting and then cold rolled and annealed in the temperature range of 600-1300/spl deg/C. The texture of the substrates was evaluated by pole-figure and orientation distribution function (ODF) analysis. The magnetic properties were also evaluated using the physical property measurement system (PPMS). It was observed that the Ni-W substrates had a stronger cube texture and a wider annealing temperature range in which the cube texture became stable than those of the pure Ni substrate. The full-width at half-maximums (FWHMs) of in-plane texture for the Ni-W substrate were 4.42/spl deg/-5.57/spl deg/ at an annealing temperature of 800/spl deg/C-1300/spl deg/C, while that of pure Ni was 9.5/spl deg/ at 800/spl deg/C. Therefore, it is considered that the addition of W enhances the formation of the cube texture and improves the texture stability at higher annealing temperatures. In addition, the Ni-W substrates had a smaller grain size and higher mechanical strength and hardness, as compared to those of the pure Ni substrate. These improvements are probably due to various strengthening mechanisms, such as solid solution hardening and/or grain size strengthening. PPMS analysis showed that the addition of W effectively reduced the saturation magnetization in an applied magnetic field, as well as the Curie temperature.