Axial Texture Research Articles

The influence of texture on elastic and thermophysical properties of kaolin- and illite-based ceramic bodies

The influence of technological texture in illite- and kaolin-based ceramic bodies was studied on textured experimental samples. Strong texture was created by spreading (layering) a wet plastic mass. The texture was confirmed by XRD analysis. Anisotropy of Young's modulus (E), thermal diffusivity (a), and relative length changes (ε) was studied as a function of firing temperature in the interval 20–1200°C. Anisotropy was assessed based on the values of E, a, and ε in two directions – parallel (axial direction, “||”) and perpendicular (transversal direction, “⊥”) to the basal planes of illite/kaolinite crystals. Up to 500°C, the ratio E||/E⊥≈2.9 and a||/a⊥≈2.0 for the illite-based samples and E||/E⊥≈6.9 and a||/a⊥≈2.7 for the kaolin samples. Above 800°C, the anisotropy of E and a decrease, but do not disappear entirely even after the firing at 1200°C. It was found, that the firing shrinkage is more significant in transversal direction, which is more pronounced in kaolin samples. The results were compared with hand molded and extruded samples, showing a very strong axial texture in extruded samples. Compared to illite, kaolin is more prone to develop a significant technological texture.

Effect of the Strain Kind on the Texture and Microstructure of Low-Alloyed Steel

Crystallographic texture and microstructure of low-alloyed steel after twist extrusion (TE) and subsequent cold rolling along and across the TE axis were studied. The double axial cylindrical texture with axes 110 and 100 parallel to the TE axis and the vortex-like microstructure are formed in the steel during the TE. The subsequent rolling of extruded steel along the TE axis promotes the forming of typical steel rolling texture as well as the microstructure with elongated grains in rolling direction. Typical steel rolling texture as well as the equiaxed microstructure is formed in extruded steel after rolling in the direction transverse to the TE axis. The mechanisms of formation of the texture are discussed.

Effect of Processing Parameters on the Magnetic Properties and Macrotexture of a Nd13.5Fe73.8Co6.7B5.6Ga0.4Alloy Processed by Equal Channel Angular Pressing With Back Pressure

Equal channel angular pressing (ECAP) is a well-established thermo-mechanical processing technique, which could induce the $c$ -axis texture of Nd2Fe14B in a melt-spun Nd13.5Fe73.8Co6.7B5.6Ga0.4 alloy. However, the effects of ECAP processing parameters, such as temperature, back pressure (BP), and multiple-pass ECAP routes, remain unknown for this alloy. In this paper, we have investigated the effects of these processing parameters on the $c$ -axis texture formation. It is found by X-ray diffraction macrotexture analysis that the maximum intensity of (001) pole figures for the tetragonal-Nd2Fe14B phase ( $I_{\max }$ ) shows an increase from 2.7 to 4.1 m.r.d. (multiples of random distribution) by increasing the ECAP temperature from 723 to 823 K, while the difference in remanent magnetization between easy and hard directions ( $\Delta M_{r}$ ) rises from 24.0 to 41.5 Am2/kg. When the BP was increased from 0.25 to 0.5 GPa at 823 K, $I_{\max }$ showed an increase from 2.8 to 4.1 m.r.d. However, $I_{\max }$ saturated for BPs above 0.5 GPa, suggesting that BP has limited effect on the texture formation, although it is necessary for the compaction of the alloy powders. Two multiple-pass ECAP routes conventionally known as routes A and C were employed for two-pass ECAP at 823 K. It is found that route A processing is effective in enhancing the texture formation, while the texture is lost by a subsequent pressing when adopting route C. Therefore, the compaction of Nd13.5Fe73.8Co6.7B5.6Ga0.4 alloy powder using route A ECAP passes with 0.5 GPa BP at 823 K results in pronounced texture, which is beneficial for anisotropic hard magnetic properties.

Special boundaries in secondary recrystallization

In polycrystalline Fe–3% Si alloy, various stages in low-temperature anomalous grain growth are investigated by electron backscatter diffraction (EBSD). For all the samples, the magnetic induction is relatively low: B 800 = 1.62–1.72 T; that corresponds to deviation of the easy-magnetization axis [001] of the crystallites from the rolling direction by 12°–20°. The secondary-recrystallization texture is described by the orientations {110} . The small grains between the anomalously growing crystallites (the secondary-recrystallization matrix) are characterized by strongly scattered (almost axial) texture {hkl} . The orientation of the growing grains is close to disorientation Σ5 in most of the crystallites forming the absorbed matrix. The anomalously growing grains ultimately absorb crystallites with special boundaries Σ3 or Σ17b.

Synchrotron high energy X-ray diffraction study of microstructure evolution of severely cold drawn NiTi wire during annealing

Microstructure evolution of a cold-drawn NiTi shape memory alloy wire was investigated by means of in-situ synchrotron high-energy X-ray diffraction during continuous heating. The cold-drawn wire contained amorphous regions and nano-crystalline domains in its microstructure. Pair distribution function analysis revealed that the amorphous regions underwent structural relaxation via atomic rearrangement when heated above 100 °C. The nano-crystalline domains were found to exhibit a strong cold work induced lattice strain anisotropy along 〈111〉, which coincides with the crystallographic fiber orientation of the domains along the wire axial direction. The lattice strain anisotropy systematically decreased upon heating above 200 °C, implying a structural recovery. Crystallization of the amorphous phase led to a broadening of the angular distribution of 〈111〉 preferential orientations of grains along the axial direction as relative to the original 〈111〉 axial fiber texture of the nanocrystalline domains produced by the severe cold wire drawing deformation.

The Structure and Shape Memory of the Hot Extruded NiTi Alloy

The paper presents results of structural studies of hot extruded NiTi shape memory alloy that is in the B2 phase at room temperature. Texture of the alloy was determined from the X-ray diffraction measurements. It was found that in result of 60 % sample reduction (at a cross-section of a bar formed by hot extrusion) weak axial texture - type <110>B2 was formed. The volume of the grains oriented in this way was approx. 20 %. Basing on metallographic observations it was also found that the size of the grains formed as a result of the thermomechanical treatment was uniform with the average area of 1700 μm2. This information is significant from the point of view of functional properties. Hot extruded alloy revealed presence of the reversible martensitic transformation. Its characteristic temperatures were slight higher than in as-cast alloy. Moreover, the extruded NiTi alloy showed 100 % of the shape recovery.

Giant Young’S Modulus Variations in Ultrafine-Grained Copper Caused by Texture Changes at Post-Spd Heat Treatment / Gigantyczne Zmiany Modułu Younga W Ultra Drobnoziarnistej Miedzi Spowodowane Przez Zmiany Tekstury W Trakcie Obróbki Cieplnej Po SPD

The effect of annealing on dynamic Young’s modulus, E, of ultrafine-grained (UFG) copper obtained by combined severe plastic deformation (SPD) is investigated. It is established that Young’s modulus in the SPD-prepared samples exceeds that in the coarse-grained fully annealed (CGFA) samples by 10 to 20 %. Isothermal annealing at elevated temperatures between 90 and 630°С leads to a sharp decrease of Young’s modulus for annealing temperatures above 210°С. After annealing at 410°С, the value of E reaches its minimal value that is 35 % lower than E in CGFA samples (total change in E is about 47 % of the initial value). Further annealing at higher temperatures leads to an increase in Young’s modulus. It is shown, that the unusual behavior of Young’s modulus is caused by formation of the <111> axial texture in the SPD-treated samples which then is replaced by the <001> texture during the post-SPD heat treatment.

Study of structural and dimensional characteristics of the melt spun p-Bi0.5Sb1.5Te3 powders compacted by vacuum hot pressing and spark plasma sintering

P-type thermoelectric Bi0,5Sb1,5Te3 powders were obtained by the melt spinning technique (extremely rapid quenching from the liquid state) and their structural and dimensional characteristics were characterized. The crystallographic group and the lattice parameters of the powders correspond to those for Bi0,5Sb1,5Te3 crystallized in equilibrium conditions which suggests the identity of the crystal structure. The powders were compacted by vacuum hot pressing and spark plasma sintering. We found that the partial axial texture [001] directed along the axis of pressure application could be formed during the compacting of the powders. Temperature dependences of the thermoelectric characteristics of the compacted material were measured in a direction perpendicular to the pressure application axis in the 100–700K range. It is demonstrated that the compacted samples possess low thermal conductivity while retaining the Seebeck coefficient and the electrical conductivity values comparable to crystallized material; therefore ZT reaches 1.05–1.15 in the 330–350K range which indicates high prospects of applying these technologies.

Electroplastic wire drawing: A promising method of production of lightweight wire and cable

This paper presents the results of studies on the drawing of copper and steel wires by different technologies: conventional, warm (heated by alternating current), and electroplastic (under the action of pulsed current in the deformation zone) and an analysis of its structure and physicomechanical properties. As a result of the electroplastic drawing (EPD) of copper and steel wire, the drawing force is reduced by 30–35%, electrical resistance decreases by 18–20%, a more perfect axial texture arises, and the wire plasticity increases, compared with the warm drawing. In the steel wire the content of α-phase is drastically reduced, which is mainly emitted in the surface layer in a few microns.

SmBa2Cu3O7−δ superconducting layer prepared on NiO buffer layer through fluorine-free chemical method

With energy shortage becoming increasingly severe, the application of high-temperature superconducting material is a considerable prospects, where economic, efficient and energy-saving preparation technology becoming the key factors for the large-scale applications of [Formula: see text] (REBCO) superconducting coated conductors. Currently, non-vacuum chemical solution deposition technique is an important way to reduce the cost of preparation of coated conductors. However, a randomly oriented NiO growth is an important problem for the non-vacuum chemical preparation of superconducting coated conductor. A simple and valid method is to prepare textured NiO film on the bare nickel (Ni) tape. In this paper, NiO films with [Formula: see text]-axis texture were prepared in air and in argon respectively by the surface oxidation epitaxial method. We obtained the smooth and densification NiO films. The layer of [Formula: see text] was fabricated on the NiO film via a fluorine-free chemistry method. The purpose of this paper is to provide a potential value of non-vacuum chemical solution deposition technique for preparation of REBCO superconducting coated conductors.

Formation of Spherulites in Electrodeposited Alloys Fe-Ni and Fe-Cr-Ni

With the use of the methods of scanning electron microscopy and X-ray diffractometry the distinctive features of spherulites creation during electrodeposition of Fe-Ni and Fe-Cr-Ni alloys from sulfate electrolyte on low-carbon steel substrate is analyzed. The presence of spherulites is detected not only in near-substrate layers of the deposits but also on the surface of quite thick (50 mm) coatings. The increase of the coatings thickness causes the increase of sperulites size due to their selective growth. The formation of sherulites occurs at quet high current density (10 A/dm2). It is shown that spherulites formation may happen on non-indifferent substrates. The interdependence of the processes of formation of spherulite structure and crystallographic texture of the nickel containing electrodeposited alloys is discovered. The formation of sperulites is accompanied by appearance of <111> axial texture of the coatings.

Latest Proofs of Validity of the Phenomenon of Phase Formation through a Stage of Liquid State in Metals Being Electrodeposited

The aim of the work was the experimental verification of the validity of the discovered phenomenon of phase formation through a stage of liquid state in metals being electrodeposited [1-3]. For that the features of formation of crystallographic texture in metals being electrodeposited under the influence of external (centrifugal) force in the directions opposite and along the texture axis were investigated. General idea for the fulfillment of new experiments was based on the fact that the degree of perfection of crystallographic texture appearing in metals being solidified from liquid state at the action of the external force significantly depends on the direction of the force action. A change of the degree of perfection of texture in metals being electrodeposited with the change of the direction of minor force action (in comparison with the value of plastic deformation creating texture in solids) will be a proof of the validity of the discussed phenomenon. Idea One and Its Realization. It is known that texture formation of metal during its solidification occurs by oriented crystallization in the direction perpendicular to the crystallization front. On the other hand, it is known that crystallographic texture of electrodeposited metal is the axial texture of growth with the axis perpendicular to the surface of a deposit. Assuming that crystallographic texture of metal being electrodeposited is formed as a result of oriented crystallization of continuously renewed metallic liquid, the action of centrifugal force directed perpendicular to the crystallization front and opposite to the texture axis will obstruct the formation of texture. The investigations of features of oriented structure formation in metals being electrodeposited in the field of centrifugal force were performed on copper and nickel samples. As a result the effect of suppression of the process of texture formation in metals being electrodeposited up to the complete disordering of crystal lattices of grains under the influence of external force in the direction opposite to the texture axis was discovered. Idea Two and Its Realization. It is known that texture formation during crystallization of metal occurs in the direction of the external force influencing the metal. At that the degree of perfection of texture of metal being solidified increases with the growth of values of the external force. Therefore, if metal being electrodeposited really passes through a stage of liquid state, then at the influence of centrifugal force on metallic liquid being solidified perpendicular to the crystallization front and along the texture axis the processes of formation and development of texture will intensify. Features of texture formation in metals being electrodeposited in the field of centrifugal force acting along the texture axis were investigated on copper and nickel samples. The effect of intensification of the texture formation process in metals being electrodeposited at the influence of external force directed along the texture axis was found. The comparative analysis of the degree of texture perfection of electrodeposited metals obtained at different directions of the force action during their phase formation was performed. It was found that regardless of the direction of the force influence the most significant change of the degree of texture perfection in metals being electrodeposited occurs at relatively low overloads. It was discovered that the action of external force in the direction opposite to the texture axis results in the more significant influence on the texture formation process in metals being electrodeposited in comparison with the force action along the texture axis. The obtained results prove the validity of the phenomenon of phase formation through a stage of liquid state in metals being electrodeposited.

Structure and phase composition of films formed by ultradispersed particles of iron and carbon

Ion-plasma sputtering and the codeposition of ultradispersed iron and carbon particles are used to create their solid solutions containing 17.6 at % carbon. Solid-solution alloys formed immediately during deposition confirm the theory of the thermal-fluctuation melting of small particles. Coating deposition is accompanied by the generation of an X-ray amorphous carbide phase, the amount of which correlates with the initial C concentration in the sample. The coating possesses an amorphous structure if the carbon content is 23.9 at %. By means of nuclear gamma-resonance spectroscopy, it is found that the magnetic moments of iron atoms are anisotropically oriented due to the formed textured coatings. The deviation of crystallite orientations from the average direction of the texture axis depends on the degree of carbonization. Pearlite eutectic (α-Fe(C) + Fe3C) arises from the amorphous phase without the formation of intermediate carbides at a temperature of 500°C. The relative cementite content correlates with the amount of carbon embedded into the coating.

Study of Structural and Dimensional Characteristics of the Melt Spun p–Bi0.5Sb1.5Te3 Powders Compacted by Vacuum Hot Pressing and Spark Plasma Sintering

P –type thermoelectric Bi 0,5 Sb 1,5 Te 3 powders were obtained by the melt spinning technique (extremely rapid quenching from the liquid state) and their structural and dimensional characteristics were characterized. The crystallographic group and the lattice parameters of the powders correspond to those for Bi 0,5 Sb 1,5 Te 3 crystallized in equilibrium conditions which suggests the identity of the crystal structure. The powders were compacted by vacuum hot pressing and spark plasma sintering. We found that the partial axial texture [001] directed along the axis of pressure application could be formed during the compacting of the powders. Temperature dependences of the thermoelectric characteristics of the compacted material were measured in a direction perpendicular to the pressure application axis in the 100—700 K range. It is demonstrated that the compacted samples possess low thermal conductivity while retaining the Seebeck coefficient and the electrical conductivity values comparable to crystallized material; therefore ZT reaches 1,05—1,15 in the 330—350 K range which indicates high prospects of applying these technologies.

Microstructure and texture of zinc deformed by extrusion with forward-backward rotating die (KoBo)

The KoBo device is a press with a cyclically rotating die enabling extrusion of ingots with the permanent destabilization of their substructure. The method involves a cyclic change of deformation path that increases the plasticity of the material and inhibits formation and propagation of cracks. The possibility of using KoBo for obtaining zinc wires with high mechanical properties was explored. A polycrystalline zinc ingot of purity of 99.995% was subjected to extrusion at room temperature. The microstructure of the material was investigated primarily via high-resolution electron backscatter diffraction using a scanning electron microscope. The microstructure is heterogeneous and consists of grains elongated slightly in the extrusion direction (ED). The material has a relatively sharp nearly axial texture with the ED scattered between the <1 0 -1 0> and <2 -1 -1 0> directions. More than 95% of high-angle grain boundaries do not correspond to any twin or low Σ CSL boundaries. The dimensions of the grains range from 10 - 20 micrometers down to the sub-micron scale. Despite the relatively large grains, the final product exhibits very good mechanical properties, which could not be explained by the Hall - Petch relation. It was found that besides grain refinement two other effects could affect the material mechanical properties. These effects are formation of nanograins inside the large, micrometer-sized grains and formation of broad areas of high-density crystal lattice defects extended along the HAGBs.

Crystallographic texture and the preferential orientation of a martensite in the polycrystalline Ni2.08Mn0.96Ga0.96 alloy

A study of the relationship of the crystallographic texture, the preferential orientation of martensite twins and the geometry changes during the martensite transformation of polycrystalline NiMnGa alloy is shown. Two states of alloy are investigated: as-cast state and the state after annealing at 923 K for 5 hours. It is shown that in the initial state the austenite phase has crystallographic axial texture <001>, while martensite has the two-component texture of the <001> and <110>. The preferential orientation of the martensitic twins in the martensitic structure is found. The crystallographic texture of the alloy after annealing is not changed, however, no preferential orientation of the martensitic twins is observed. In the martensitic phase structure martensitic twins are oriented randomly. Anisotropy of the thermal expansion during the martensitic transformation is shown, while in the annealed state such effect is not found.

Texture and anisotropy of yield strength in multistep isothermally forged Mg-5.8Zn-0.65Zr alloy

The effect of multistep isothermal forging (MIF) on microstructure, texture and anisotropy of ambient temperature yield strength of MA14 (Mg-5.8Mg-0.65Zr (%, wt)) magnesium alloy hot-pressed rod was analyzed. It has been found that the initial axial texture is quite stable under 1st MIF step up to strain e∼4.2 at 400°C and has been gradually transformed into much weaker single-peak one at further processing at 300 and 200°C to total strain of 10.2. Such texture changes were accompanied by strong grain refinement, along with significant reduction of the alloy strength anisotropy.

Development of the rotational mode of plastic deformation upon drawing of pearlitic steels of various alloying systems

Transmission electron microscopy has been used to study the evolution of the microstructure of fine pearlite in the process of drawing of a number of steels of eutectoid composition of different natural alloying complexes. A relation has been established between the development of a rotational mode in lamellar pearlite and the formation of an axial texture upon the deformation of steels containing microadditives of alloying elements.

Vibrational algorithms for quantitative crystallographic analyses of hydroxyapatite-based biomaterials: I, theoretical foundations.

The Raman spectroscopic method has quantitatively been applied to the analysis of local crystallographic orientation in both single-crystal hydroxyapatite and human teeth. Raman selection rules for all the vibrational modes of the hexagonal structure were expanded into explicit functions of Euler angles in space and six Raman tensor elements (RTE). A theoretical treatment has also been put forward according to the orientation distribution function (ODF) formalism, which allows one to resolve the statistical orientation patterns of the nm-sized hydroxyapatite crystallite comprised in the Raman microprobe. Close-form solutions could be obtained for the Euler angles and their statistical distributions resolved with respect to the direction of the average texture axis. Polarized Raman spectra from single-crystalline hydroxyapatite and textured polycrystalline (teeth enamel) samples were compared, and a validation of the proposed Raman method could be obtained through confirming the agreement between RTE values obtained from different samples.

Formation of an axial texture during drawing steel with a lamellar structure

Formation of an axial texture during drawing steel with a lamellar structure