Showing papers on "Texture (crystalline) published in 1974"

Bistability behavior of texture in cholesteric liquid crystals in an electric field

Abstract: With the homeotropic boundary condition, the field‐induced cholesteric‐to‐nematic texture transition can show a large hysteresis effect such that at the same field strength either the cholesteric or the nematic texture is stable.

The influence of grain size and impurities on the magnetic properties of the soft magnetic alloy 47.5% NiFe

Abstract: An attempt has been made to equate quantitatively the coercive force as a function of the grain size and the concentration of nonmagnetic inclusions. It was found that the coercive force H c of recrystallized 47.5% nickel-iron can be completely described, independent of the final anneal temperature, by the grain size d K and the inclusion content N F . Only nonmagnetic inclusions of sub-micron size (0.02- 0.5 μm) were found to be of significance. A definite correlation between the coercive force of 47.5% nickel-iron and those inclusions visible using an optical microscope (> 1μm) was not observed. Furthermore, there was no clear dependence of the coercive force on the sulfur and oxygen content. The grain size term H cK was found to be in good agreement with the theory of A. Mager [1]. Surprisingly, there was no difference between the low-angle grain boundaries of strip with cube texture and the large-angle grain boundaries of un-textured strip with respect to H cK .

Structure/property relationships in evaporated thick films and bulk coatings

Abstract: This paper reviews the known data on structure/property relationships in thick films or bulk coatings of metals, alloys, and compounds produced by high-rate evaporation/deposition technology. The effects of process variables (depostion temperature and/or kinetic energy of depositing atoms) on the microstructure, texture, and mechanical properties is given. The influence of coatings on corrosion resistance and thermal fatigue is also stated.

Anomalies in Measurement of Residual Stress by X-Ray Diffraction.

Abstract: : Residual stresses are expected to lead to a linear dependence of the interplanar spacing, d, on sine squared psi (where psi is the sample tilt) and the stress can be obtained from the slope of this line. As a result of the linear dependence a two-tilt method is often employed to obtain the stress. However, when a specimen is subjected to extensive plastic deformation large deviations from a straight line can occur and a two-point method can lead to an erroneous stress determination. The results reported here show that: (1) this is more likely to occur in homogeneous materials than in multiphase materials (2) the oscillations follow closely the variation in peak intensity due to texture (3) the oscillations are caused by microstresses which are due to an 'orientation' effect as suggested by Weidemann. A simple, easy-to-use procedure has been developed and tested to correct the data and obtain the correct macrostress. The materials used were Armco iron, steel and ordered Cu3Au. (Modified author abstract)

Method of making a dry-type pet food

Abstract: A method is described for producing a dry pet food having a moisture content of less than 15 percent by weight. Its texture may be substantially solid and fibrous or it may be expanded. The pet food contains a reduced amount of amylaceous ingredients as well as specified types of proteinaceous adhesives in conjunction with plasticizing agents, and is processed to form either a fibrous or an expanded texture using a specially designed air nozzle.

The Development of the Rolling Texture of Iron Determined by Neutron-Diffraction

Abstract: The development of the rolling texture of a low carbon steel was investigated by neutron diffraction calculating three-dimensional orientation distribution functions. The textures consist of two limited fibre axis components A and B centered about (1¯1¯1)[1¯21]

Method of producing doubly oriented cobalt iron alloys

Abstract: An alloy and process are described for obtaining improved magnetic characteristics in iron-cobalt alloys. The iron-cobalt alloys described are characterized by a cube-on-face texture, primary recrystallized and normal grain growth microstructure. Processes are described which include both a single stage cold working and a multiple stage cold working in order to obtain the desired texture in the finished alloy.

Light Scattering from Polymer Films Having an Optically Anisotropic Rod-Like Texture in Relation to a Model of a Random Assembly of Disordered Rods

Abstract: Light Scattering from Polymer Films Having an Optically Anisotropic Rod-Like Texture in Relation to a Model of a Random Assembly of Disordered Rods

Study of deformation in polytetrafluoroethylene by x‐ray line broadening

Abstract: The effect on PTFE of crystallization conditions and subsequent tensile deformation have been examined by Fourier analysis of the shapes of diffraction peaks. Crystal perfection increases with decreasing rate of cooling from the melt. During deformation, the crystallite size is reduced drastically in the range of strain from 35 to 185%. The microstrains are not altered over this range, implying crystal breakup rather than distortion within crystallites. It is in this range that previous studies with the same specimens have indicate a sharp transition in texture. The fact that root‐mean‐square (rms) microstrains increase due to elongation suggests that the crystalline regions not only break up but that they are also deforming plastically. Electron microscopic investigation indicate that the striation spacing on crystals in the fracture faces is much smaller than the crystallite size measured with x‐rays; thus the striations do not represent alternating crystalline and amorphous regions.

Structures and properties of vacuum vapor deposited coatings on steel substrates

Abstract: An examination was made of the influence of some deposition parameters on coating structures and properties. The evaporated metals were aluminum and zinc. The deposition parameters were deposition rate and substrate temperature and roughness. The examined coating properties were appearance, adhesion, grain size, porosity, texture, and structure. The coatings were applied on steel sheets and wire pieces in a discontinuous way, and on wire in a continuous air-to-air installation. In testing the zinc coatings, the influence of both, the substrate temperature and the deposition rate on coating grain size and porosity, was most evident. Also the influence of the deposition rate on the re-evaporation temperature of the substrate was examined. During the examination of the aluminum coatings, an important influence of deposition rate and substrate temperature on structure, grain size, texture, and condensation mechanism was established.

Properties of ZnS Films Evaporated in High Vacuum

Abstract: Thin films of ZnS made by evaporation in high vacuum were investigated by different analytical methods. The changes in chemical composition, crystal structure, texture, density and refractive index of these films are shown as a function of film thickness.

Embossed needle-bonded fabric wall coverings

Abstract: A non-woven material is applied to the surface of a woven scrim. The non-woven material is needle-bonded to the scrim. The composite structure is then embossed. The embossed pattern is placed by a heated embosser on the finished product and in the non-embossed areas, the heat of embossing causes the non-woven material to partially melt and assume a textured effect which mirrors the texture of the woven scrim.

Preferred orientation in powder samples of magnesium and magnesium-cadmium alloys

Abstract: Cylindrico-symmetrical needle-type texture has been observed in powder samples of magnesium and magnesium-cadmium alloys. Orientation distributions of crystallites determined by measurements of 002 reflexions on texture goniometer can be described by simple analytical expressions. Corrections for preferred orientation applied to measurements on powder diffractometer enable determination of Debye characteristic temperature≡ from the dependence of intensities on diffraction angle. The values of≡ determined after correction from samples with preferred orientation are in agreement with the value of randomly oriented sample.

The Development of Rolling Texture in α-Brass Determined by Neutron Diffraction

Abstract: The three-dimensional orientation distribution was calculated from neutron diffraction pole figures for a copper 27.2% zinc alloy cold rolled to different degrees of deformation. The results agree qualitatively with those of other authors. There are however differences in the quantitative respect which influence the conclusions to be drawn. For rolling degrees lower than about 70% the texture exhibits an orientation tube similar to that of the copper type, but with a significantly different distribution along the tube axis. For rolling degrees larger than 70% the texture can be described by the orientation { 110 } 〈 112 〉 . The deformation is assumed to occur according to the Wassermann model and the Hu model respectively in these two ranges.

Copper microwires spun from the melt

Abstract: To obtain metal fibres of diameter less than 50 μm, the Taylor method has been developed for copper microwires to exploit their electrical and electronic applications. We have tested the dependence of continuity, grain size, texture and mechanical properties on the process parameters as well as drawing ratio and quenching time. Grain arrangement and the elastic-plastic behaviour of the fibres are discussed.

Crystalline texture of injection-molded nylon 6

Abstract: Injection-molded specimens of nylon 6 were examined by x-ray diffraction as a function of depth in three characteristic directions. A skin and a core were always found to be present which differed in the degree of crystalline perfection and crystal modification. While the core of pure nylon 6 was found to be not oriented, the core of specimens containing nucleating agents was found to contain a typical texture of the monoclinic modification of nylon 6 in which the distribution probability of the a* and c* axes resembles ellipsoids with three unequal axes. A model explaining this texture as due to degenerated (deformed) spherulites is proposed. With a transcrystalline nylon 6 specimen the direction of the fastest growth in the unit cell (which forms the radius of spherulites) is found to be close to the a axis.

The structure and mechanical properties of polyoxymethylene polymerized in the solid state

Abstract: Polyoxymethylene specimens with single crystal texture were produced by irradiation of needle-shaped trioxane crystals subsequently post-polymerized at fixed temperatures between 30 and 60°C. A clear dependence of polymer conversion on irradiation dose and polymerization temperature was revealed. The polymer morphology consisted of mutually aligned fibrils, half of which were chain-extended crystallites with their molecular axes coincident with the specimen axis. The remaining fibrils consisted of folded chains in a “twin” configuration. The degree of order in the specimens was analysed in terms of the arcing of X-ray diffraction spots. There existed an intrinsic level of misorientation of molecules which depended on the post-polymerization temperature, plus a misalignment due to displacement of fibrils on the removal of unreacted monomer. Finally, the mechanical properties were investigated and the Young's modulus was found to approach closely its theoretical limit at the conversion maximum. The results are interpreted on the basis of a simple morphological model.

Influence of machining temperature on the surface damage, residual stress, and texture of hot-pressed beryllium

Abstract: The effect of lathe machining temperature ranging from room to 400°C on the depth of twinning, extent of microcracking, residual stress, and texture of hot-pressed, S200-type beryllium was investigated. It was shown that twinning, microcracking, and residual stress were essentially eliminated when machining was performed above the ductile-to-brittle fracture transition range at 400°C. This behavior has been related to the operation of multiple slip systems, which, in terms of the von Mises criterion, satisfies the condition for uninhibited deformation. Minimization of residual stress was attributed to recovery resulting primarily from dislocation annihilation and climb, the latter giving rise to the formation of welldefined low-angle boundaries and stable hexagonal networks adjacent to the machined surface.

Investigation of the Anisotropic Anodic Polarization Behavior of Titanium

Abstract: Anodic polarization measurements have been made potentiostatically on single crystal and polycrystal titanium in 1N H2SO4 at 23 C (73 F). Three low index surfaces, (0001), (11 2 0), and (10 1 0) were studied together with polycrystalline rolled sheet material. A strong influence of crystallographic orientation on the anodic current densities was found in both the active and the passive regions. The most active surface was (11 2 0), the least active (0001). The most passive surface was also (0001), unless the specimen had been in a cathodic region, whereupon that orientation became the most reactive. That effect and others that are associated with titanium hydride formation are discussed. The effect on the reactivity of the polycrystalline surface due to preferred orientation texture is mentioned.

Morphology of melt-drawn polyethylene films investigated by transmission electron microscopy

Abstract: Melt-drawn polyethylene fibers have been investigated by transmission electron microscopy and electron diffraction. Depending on the drawing procedure, different morphologies have been observed. In the material drawn at a temperature of the melt of 155°C, a strong fiber texture was obtained. In the material drawn at lower temperatures, a second supermolecular structure was found. This second structure was attributed to the presence of small crystallites or of crystalline aggregates embedded in the oriented material. The size of the crystallites or crystalline aggregates ranges from 100 A to a few microns. A model of these two coexisting supermolecular structures is proposed to account for the above observations.

Apparatus for Routine Measurement of Food Deformation in Texture Tests at Low Deformation Rates

Abstract: Two systems are described for measuring food deformation in texture tests. The time required for the applied force to change a selected amount is automatically displayed on a digital pulse counter. Since the deformation rate is constant deformation can be derived. The deformation rates that can be used for testing products ranging in firmness from 272 to 5377 g/min is established. Under certain conditions rates up to 100 cm/min can be used without introducing large errors. The readout device is suitable for applications where large numbers of samples must be tested with minimum labour.

Ultrasonic spectroscopy applied to double refraction in worked metals

Abstract: An experiment has been performed showing that ultrasonic spectroscopy can be used to study texture in worked metals and other textured polycrystals. Echoes from a broadband shear transducer polarized at 45° between two characteristic directions in a rolled aluminum specimen showed nulls in their spectrum corresponding to differences of (2 n − 1)π in phase between the components of the wave amplitude resolved along the characteristic directions. From the frequencies of the nulls, the fractional velocity difference Δv/v was computed to be 0.021, a reasonable value for aluminum with moderate texture. Ultrasonic spectroscopy is particularly useful to study texture when the first echo contains several nulls, i.e., n > 1 in the phase difference (2n − 1)π.

Changes in microstructure of oriented Ba3Co2Fe24O41 material during sintering. II

Abstract: Pellets of the ferrimagnetic material Ba3Co2Fe24O41 were sintered at temperatures between 1220°C and 1310°C in (1) a non-oriented state, (2) with a fibre texture generated by a rotating magnetic field during pressing and (3) with a fan texture due to a static magnetic field. During sintering up to 24 h. the changes in texture sharpness and density were studied. Textured samples attained a higher ultimate density than non-oriented ones and those with fibre texture became densest. To determine the sharpnesses of the texture the maximum standardized intensities of the reflexions 0′0′0′14, 1′0′\bar 1′16, 1′1′\bar 2′10 and 11\bar 20 were calculated from the experimental intensities. The mutual relations of the maximum standardized intensities of the four reflexions were given by representing the intensities of these reflexions for both textures as polynomials. The dependence of sharpness of texture on position in the pellet has been determined. It followed that this sharpness had to be averaged over the height of the pellet, to get a representative value for the whole pellet. Both kinds of texture were found to sharpen during normal grain growth, but during exaggerated grain growth in the last stage of sintering the sharpness of the fibre texture decreased, whereas that of the fan texture still increased. A possible explanation of this phenomenon is given on the basis of the different characters of these textures. A linear relationship is found between sharpness of texture and area porosity during normal grain growth. The compound starts decomposing at a lower temperature than that given in literature.