Formation Of Preferred Orientation Research Articles

Mechanism on the nucleation of orientation-preferred Cu6Sn5 at different temperatures and solder compositions

In this paper, the mechanism on the nucleation of orientation-preferred Cu6Sn5 at different temperatures and solder compositions was investigated. Results suggest that affected by temperature and solder composition, the distribution of clusters in solder plays an important role in the formation of preferred orientation. Higher temperature, Ag element and an appropriate amount of Cu element are favorable for the nucleation of orientation-preferred Cu6Sn5. However, the increase of Cu-Sn clusters size with the increase of Cu addition will lead to the nucleation of Cu6Sn5 in liquid solder, which does not need to follow the rule of the minimal lattice mismatch between Cu6Sn5 and Cu substrate. Meanwhile, the addition of Cu and Ag is conducive to the increase of grain size. Besides, the difference in solder volume between the central and edge region results in the difference in grain orientation. Furthermore, a model is established to illustrate that how the reflow temperature, Cu and Ag content affect the nucleation of orientation-preferred Cu6Sn5 through affecting the cluster evolution. The results have significant meaning in understanding and controlling the formation of Cu6Sn5 preferred orientation and improving the reliability of solder joints.

Investigation on growth of the orientation-preferred Cu6Sn5 on (001)Cu during the temperature-increased multiple reflow process

The preferred orientation of Cu6Sn5 formed on (001) Cu single crystals has attracted great attention due to its feature of strong anisotropy. Lots of researchers believe that the formation of preferred orientation is closely related to the reaction temperature but do not have a unified conclusion. In this study, a temperature-increased multiple reflow process was designed and utilized to investigate the grain rotation and coarsening behavior of orientation-preferred Cu6Sn5 formed at the Sn-3Ag/(001)Cu interface. Results demonstrate that the temperature-increased multiple reflow process facilities the annexation and rotation of Cu6Sn5 grains as well as their morphology transformation from scalloped-type to small facet. The results have significant meaning in understanding and controlling the formation of Cu6Sn5 preferred orientation and improving the reliability of solder joints.

Application of the capillary method in micro X-ray diffractometry (µ-XRD): A useful technique for the characterization of small amounts of clay minerals

AbstractThe laboratory micro X-ray diffraction (μ-XRD) technique is a suitable method to study minerals in-situ in whole-rock specimens without any sample preparation or in polished thin sections, and even in small amounts in powdered form. The micro X-ray diffraction method uses the conventional, closed-tube X-ray generator, but modifications were needed in the diffraction column, sample holder and detector in order to achieve μ-XRD capability.In this paper, we present a case study of the capillary method used in µ-XRD on hydrothermal clay mineral assemblages that formed in the Velence Mts (Hungary). The capillary method in µ-XRD has many advantages in the investigation of small amounts of clay minerals: (1) easy and rapid preparation of randomly oriented, powdered samples; (2) rapid measurements; (3) accurate diffraction patterns. By using the capillary method, the formation of preferred orientation can be eliminated; thus the (hkl) reflection of the clay minerals can be precisely measured. Illite polytype quantification and the investigation of (060) reflection of clay minerals can be used satisfactorily in µ-XRD.Hydrothermal clay mineral assemblages are indicative of temperature and pH. Their examination can determine the physicochemical parameters of the hydrothermal fluids that interacted with the host granite in the Velence Mts. The analyzed hydrothermal clay minerals from the western part of the mountains suggest lower temperatures (150–200 °C) and intermediate pH conditions. In contrast, the clay mineral assemblages' characteristics for the eastern part of the mountains indicate more intense argillization and higher temperatures (∼220 °C) and intermediate pH conditions.

Preferred orientation formation in surface layer of aluminum sheet subjected to friction roll surface processing and temperature gradient annealing

Preferred orientation formation in surface layer of aluminum sheet subjected to friction roll surface processing (FRSP) and temperature gradient annealing has been investigated by SEM/EBSD analysis. FRSP imposed severe shear strain in the surface layer of the aluminum sheet, where the indentation was selected as 0.1mm and the feeding speed was set as 0.3mm/s. The annealing with steep temperature gradient in longitudinal direction was applied to the small specimen of 12mm long, 10mm wide and 1mm thick, which made microstructural evolution concentrated to the nearest layer to the surface. Shear strain more than 10 was imposed at a site of 14μm beneath the surface. The temperature gradient more than 20K/mm was attained even for aluminum which has high thermal conductivity. The {100} pole of ND/TD (FRSP plane/FRSP direction) FRSPed specimen showed very weak intensity of <001>//ND while the {111} pole implies <110>//TD. In contrast, the shear texture component {111}<110> mainly evolved in the specimen subjected to FRSP and the ordinary annealing. Evolution of the component {111}<110> after the temperature gradient annealing were compared with that after the ordinary annealing in consideration of stored strain energy in each crystallographic orientation.

Preferred orientation formation in Al-3mass%Mg subjected to shear deformation and subsequent annealing

Shear deformation is imposed on materials by several advanced techniques for microstructural and textural control. Shear texture evolved during deformation tends to remain after subsequent annealing. Preferred orientation formation with shear deformation and annealing in Al-3mass%Mg alloy rolled sheet has been investigated by SEM/EBSD technique. S-shaped specimen was prepared from the alloy sheet to impose shear strain in compression. The central objective part of the S-shaped specimen was sheared with rotation about the normal axis so as to develop preferred orientations of {111} parallel to the original shear plane and <110> parallel to the original shear direction before deformation. In-situ EBSD analysis revealed that the preferred orientations formed by shear deformation remain and evolve as recrystallization texture during subsequent annealing. The evolution of the shear recrystallization texture depended obviously upon sample direction parallel to shear direction.

Highly porous spark plasma sintered Ni-Mn-Ga structures

A new approach for the processing of porous crystalline Ni-Mn-Ga compacts by spark plasma sintering (SPS) from a mixture of gas atomized Ni-Mn-Ga and NaCl powders (25/75vol%) is reported. The NaCl was removed to reveal a highly porous skeleton of Ni-Mn-Ga. Solid skeletons were heat-treated in vacuum to grow the grains to a size of 22–23μm, from the 1.7μm found in the powder. The sample with the highest porosity showed a magnetic-field-induced strain of 1.24%. The MFIS is attributed to magnetically induced twinning due to the reduction of grain boundary constraints and the formation of preferred orientation.

Understanding of Preferred Orientation Formation in Rock-Salt Materials: The Case of MgO

We developed a kinetic model to predict the preferred orientation for the case of rock-salt MgO crystal by assuming random walk diffusion of the adatom between (111) and (100) planes during growth. This model suggests that the tendency of the (111) preferred orientation increases under high deposition rate and low activation energy for diffusion of the adatom between (111) and (100) grains because the adatoms on the (111) surface stick to the surface more strongly compared to those on the (100) plane. The theoretical model was confirmed experimentally by growing several polycrystalline MgO films using the electron beam evaporation method. We could easily control the flux and energy of MgO adatoms by modulating the emission current of the electron gun, substrate temperature, and extra energy source such as ion beam assisted deposition. Our experimental results show good qualitative agreement with the model for the various polycrystalline MgO films deposited at several growth conditions.

Computer modeling of texture formation processes in Ti Grade 4 during continuous equal channel angular pressing

This work presents the results of computer modeling of crystallographic texture evolution in the volume of Ti Grade 4 billets subjected to continuous equal channel angular pressing (ECAP) at a temperature of 200°С, with a number of passes from 1 to 8 via the ВС route. Regularities of preferred orientation formation have been stated, and the activity of some or other slip and twinning systems in Ti billets has been evaluated against the number of ECAP passes. The obtained results explain and allow predicting the behavior of nanostructured Ti Grade 4 with account of the parameters of its microstructure and crystallographic texture. The obtained modeling results are compared with the results of experimental X-ray studies.

Microstructure and through-film electrical characteristics of vertically aligned amorphous carbon films

The microstructure and electrical properties of in-situ annealed carbon films is studied in this paper. In-situ annealing (150 °C to 600 °C) was done during the deposition of carbon films with −300 V substrate bias. Transmission electron microscopy and two points electrical probing studies were performed and the deduced transition for vertical orientated graphitic planes occurs at temperatures above 400 °C. The microstructure of the films strongly depends on the deposition temperature of the films (room temperature, 400 °C and 600 °C). Electrical conductivity of the film strongly depends on texturing due to the formation of preferred orientation in the vertical direction. The vertically orientated carbon (VOC) sheet provides effective nanochannels for electron transport, thus significantly improves the electrical properties of the annealed film.

Plasma density induced formation of nanocrystals in physical vapor deposited carbon films

The effect of plasma parameters on the nanostructures formed during physical vapor deposition growth of carbon films has been studied. It was shown that the formation and nature of nanostructures strongly depend on plasma density and ion energy during the deposition. High plasma density results in formation of nanocrystals with preferred orientation even at low negative substrate bias (300 V) while at low plasma density higher substrate bias (500 V) is required for the nanocrystals. Moreover, at the same plasma density the nature of the nanostructures strongly depends on the ion energy. At higher ion energies, carbon nanotubes are formed in the microstructure while at lower ion energies, graphitic nanostructures are more stable. It was also found that prior to the formation of preferred orientation, an amorphous layer is formed at the silicon/carbon interface. Through electron energy loss spectroscopy, it is shown that the structure of this layer strongly depends on ion energy during the deposition.

Growth Mechanism of MgO Film on Si (100): Domain Matching Epitaxy, Strain Relaxation, Preferred Orientation Formation

We present the growth mechanism of MgO film on Si (100), specifically, epitaxial growth at the interface, strain relaxation at critical thickness, and preferred orientation formation after strain r...

Preparation of polycrystalline BaTi 2O 5 ferroelectric ceramics

Polycrystalline BaTi 2O 5 (BT 2) was prepared by solid state sintering in air using BaCO 3 and TiO 2 as starting materials. A rod-like BT 2 sintered bodies in a single phase were obtained above 1025 °C by adding 5 wt.% B 2O 3. The densification of BT 2 sintered bodies decreased with increasing sintering temperature. The maximum permittivity of BT 2 sintered body was 640 at the Curie temperature ( T c) of 461 °C and the frequency of 100 kHz. The addition of B 2O 3 was effective to obtain BT 2 in a single phase at low temperatures with elongated microstructure and to improve the permittivity, indicating the formation of preferred orientation at low temperature was related with liquid-phase sintering mechanism.

26.2: Preferred Orientation Formation of MgO Layer during Ion Beam Assisted Deposition Process

AbstractMgO films deposited on Si (111) and Al2O3 (0006) substrate have only (111) diffraction independent of film thickness while those on Si (100) substrate have preferred orientation change from (200) to (111) as film thickened due to the highest adatom mobility of (200) plane. By using ion beam assisted deposition, the crystal structure of MgO could be controlled via adjusting adatom mobility.

Formation of preferred orientations in aluminum, copper, and nickel irradiated with intense ion beams

The formation of preferred orientations in metal targets under exposure to intense ion beams was studied using x-ray diffraction. The formation of axial textures with [111] and [100] axes, observed in aluminum, copper, and nickel samples, depends on both the ion current density and thermal characteristics of the target material. In the case of rapid propagation of the thermal front to the material depth, the texture is apparently formed by the dislocation mechanism, which occurs in copper samples having the highest thermal conductivity. For aluminum and nickel, the most probable are recrystallization and regrowth mechanisms, respectively. An analysis of inverse pole figures showed that the main direction of heat sink in textured samples corresponds to the normal to the (111) atomic plane.

Energy- and Momentum-Resolved Exchange and Spin-Orbit Interaction in Cobalt Film by Spin-Polarized Two-Electron Spectroscopy

Spontaneous ordering of electronic spins in ferromagnetic materials is one of the best known and most studied examples of quantum correlations. Exchange correlations are responsible for long range spin order and the spin-orbit interaction (SOI) can create preferred crystalline directions for the spins, i.e., magnetic anisotropy. Presented experimental data illustrate how novel spin-polarized two-electron spectroscopy in-reflection mode allows observation of the localization of spin-dependent interactions in energy-momentum space. Comparison of spin-orbit asymmetries in spectra of Co film and clean W(110) may indicate the presence of interface specific proximity effects providing important clues to the formation of preferred orientations for the magnetic moment of the Co film. These results may help to understand the microscopic origin of interface magnetic anisotropy.

Study on Preferred Orientation in Nd-Fe-B Cast Strip

The reason for high intensity of (006), (004) and (008) peaks on the free surface in Nd-Fe-B cast strips was studied. The formation of preferred orientation in Nd-Fe-B cast strips was discussed. The analysis shows that the combined effect of both hot deformation and preferred crystal growth leads to the c axis perpendicular to the wheel surface.

Crystallographic Relationships between FCC and BCC Crystals: A Study Using EBSD Techniques

The mechanisms governing the formation of transformation textures during the austenite-to-ferrite transformation are the subject of major debate. In this study, two extreme cases were examined: those of undeformed and deformed austenite. The first involves the transformation of austenite into Widmanstätten ferrite under "equilibrium" conditions in the Gibeon iron-nickel meteorite. This meteorite passed through the transformation at the rate of a few degrees per million years. Such cooling rates cannot of course be reached under laboratory conditions. The second concerns the transformation of hot rolled austenite after a quench into the bainite temperature range. These two behaviors were investigated by means of optical microscopy and electron backscatter diffraction (EBSD) techniques. The orientations of both the parent and product phases were measured and the orientation relationships are represented in Rodrigues-Frank (R-F) space. From the orientation of a particular FCC crystal, the crystallographic orientations of the product BCC crystals can be predicted according to the Bain, Kurdjumov-Sachs (K-S) and Nishiyama- Wassermann (N-W) correspondence relationships. Comparison of the predicted and measured orientations reveals that the Bain rotation is never observed; the K-S and N-W relationships are both observed and there is a continuous distribution of orientations between the exact K-S and N-W positions. The formation of preferred orientations under non-equilibrium conditions is scrutinized. These results are compared to recent models accounting for variant selection.

Preferred Orientation Formation in Sheets Worked by Continuous Cyclic Bending

Preferred Orientation Formation in Sheets Worked by Continuous Cyclic Bending

Thermodynamic theory for preferred orientation in materials prepared by energetic condensation

In this paper, some general observations are made concerning the formation of preferred orientation in thin films deposited from the vapour phase, and also in the case where some of the depositing atoms or ions have greater than thermal energies. As a general principle, we postulate that the structures observed represent a minimum of energy for the set of configurations available to the system. The contributions to the energy arise from surfaces and interfaces as well as from the elastic strain energy in the bulk. The implications of this postulate are studied with reference to the growth of BN and related materials including AlN and amorphous carbon.

Compressive stress induced formation of preferred orientation in glassy carbon following high-dose C+implantation

Abstract It is well established that ion irradiation of glassy carbon with energetic ions leads to the formation of a dense amorphous surface layer. In the present work we show using cross-sectional Tem that oriented graphite-like regions are formed within the implanted layer of glassy carbon implanted with 50 keV C ions at high doses. The preferred orientation is such that the sp2 bonded graphite-like sheets lie normal to the implanted surface. Stress measurements of the implanted material show the presence of a biaxial compressive stress. Thermodynamic calculations predict that a non-hydrostatic stress can result in preferred orientation in anisotropic materials such as graphite. The preferred orientation can therefore be explained in terms of the combined effects of the mobility introduced by the implanted ions and the anisotropic stress field.