Papers by Keyword: Crystal Orientation

Abstract: Microstructures and tensile properties at 233 K, 300 K and 398 K of Sn-3.0 mass%Ag-0.5 mass%Cu (SAC305) and Sn-Ag-Cu-In-Sb solder were investigated by using miniature size specimens with 0.5 mm diameter, which can reproduce the microstructure of the real solder joint. In this study, three kinds of Sn-Ag-Cu-In-Sb solder (SAC305-6.0 mass%In-1.0, 2.0 and 3.0 mass%Sb) were used. The microstructure of SAC305 consisted of a single crystal grain. On the other hand, the microstructures of Sn-Ag-Cu-In-Sb solder consisted of polycrystalline. The number of crystal grains per the cross section of SAC305-6.0In-1.0Sb was stably several tens or more. The tensile strength of Sn-Ag-Cu-In-Sb was improved approximately 2 times that of SAC305. Also, the variation in tensile strength of SAC305 at 233 K was large due to anisotropy of the crystal grain. In contrast, the variation in tensile strength of Sn-Ag-Cu-In-Sb at 233 K was lower than that of SAC305. In particular, that of SAC305-6.0In-1.0Sb was reduced to approximately a sixth of that of SAC305. It seems that the effect of anisotropy of the crystal grain is decreased by polycrystallization in SAC305-6.0In-1.0Sb.

Abstract: In this study, a novel formulation of phase field model for representing solidification of polycrystalline metals is proposed. A quaternion-based crystal orientation representation is introduced into the KWC-type phase field model. Using this approach, three-dimensional rotation of crystal orientation can be represented by a direct extension of the conventional KWC model. A numerical simulation by the presented model is conducted, and the characteristics and adequacy of the model are discussed.

Abstract: In the telescopic interferometer KAGRA (Large-scale Cryogenic Gravitational wave Telescope), the ultraprecision mirror made of sapphire (α-alumina) is required to polish. The focal length of the mirror is 7 km and it must be finished by polishing after grinding. In order to polish the mirror precisely, polishing characteristics of the sapphire must be researched. In this study, the polishing characteristics are examined and the dependence of the crystal orientation on the polishing rates is studied. In the experiments, sapphire wafer is polished by using rotational small tool and SiO₂ abrasives.

Abstract: Plasticity zone at crack tip of aluminum alloy with fcc structure is investigated in order to analyze the effect of crystal orientation to the plasticity distribution on crack tip, as well as the effect to CTOD and J-integral, which is implemented using finite element code in Abaqus with a rate dependent crystal plasticity theory. The results show that the crack tip plasticity, stresses and CTOD are significantly affected by grain orientations. When the grains have single textures, Cube and S orientations have a strong ability to against crack propagation. However, when the grains combine textures, the increasing of misorientation enhances the resistance for crack growth. And when the tilt angle is higher, the crack deflection is promoted to reduce the crack propagation rate.

Abstract: In order to clarify the mechanical properties of single-crystal silicon carbide (SiC), nanoindentation was performed on a 4H-SiC wafer. The change of hardness with the angle between the wafer orientation flat and the indenter edge, the maximum load and the loading rate were investigated. The hardness reached maximum at an indentation load of 12 mN in the range of 3-50 mN. Hardness decreased under two conditions: when the edge of the indenter tip is parallel to the [11-20] direction, and when a very low loading rate was used. Transmission electron microscopy was used to observe dislocations and cracks under the indents. It was demonstrated that the deformation process of SiC involved three steps with respect to the increase of the indentation load. These results provide information for improving ductile machining process of single crystal SiC.

Abstract: The high temperature ultra-high cycle fatigue (UHCF) behaviors of DZ125 superalloy used in aero-engine turbine blades were systematically studied. The results show that the fatigue fracture still occurs above 10⁸ at the frequency of 20kHz, R=-1 and 700°C. There is a negligible frequency effect for the DZ125 superalloy, therefore, it is proposed that the ultrasonic fatigue testing could be expected as an accelerated fatigue testing method. Fatigue cracks originate from the subsurface of the specimens, where have no metallurgy defects or “fish eye” character. The crystal orientation change of the alloy is very little after fatigue.The maximum value changed for the elastic modulus of the alloy is about 30GPa after fatigue compared with that before fatigue.

Abstract: The influence of the crystallographic orientation, the level of axial strain and the test temperature on the progressive cross-section ellipticity of single crystal samples under uniaxial tension is analyzed in order to improve axial strain measurement in experiments. The direct three-dimensional finite element modeling of elasto-plastic deformation process of single-crystal initially cylindrical samples is used with taking into account finite strains, slip mechanisms and necking.

Abstract: Electrodeposited silver layers obtained from high-cyanide silver plating solution are widely applied for connectors and switches of automobiles. However, few groups have discussed the relationship between the crystal structure of silver layers and their properties. In this study, the effect of the concentration of Se, added as a brightener to high-cyanide silver plating solution, was investigated by XRD and EBSD analysis for electrodeposited silver layers with {200} orientation. By optimizing the concentration of Se in the silver plating solution, the {200} orientation ratio of the silver layer was increased to as high as 94%. Since the diffusion of Cu from the Cu substrate used in this study into the silver layer was inhibited, the silver layer with the high {200} orientation ratio exhibited good electrical contact resistance of the surface of 1.3mΩ after a heating test performed at 200°C for 74h. In addition, the silver layer had good bend formability. The results of XRD analysis confirmed that the recrystallization of the electrodeposited silver layer occurred at room temperature within several hours, thus increasing the {200} orientation ratio of the silver layer.

Abstract: The coarsening behavior of Cu₆Sn₅ grains formed at the Sn37Pb/Polycrystalline Cu interface is investigated in terms of their orientation evolution during solid-state aging. The results show that the coarsening behavior of the interfacial Cu₆Sn₅ grains during solid-state aging are quite different from that during liquid-state soldering. The occurrence of the coarsening in the solid-sate reaction is caused by the different surface energies between two adjacent grains. In addition, the texture morphologies of the interfacial grains affect their coarsening rates. In particular, the interfacial Cu₆Sn₅ grains formed at 200 oC exhibit a texture with the [0001] direction normal to the interface after 16 days of aging at 150 oC, and the formation of this texture accelerates the coarsening process of the interfacial Cu₆Sn₅ grains.

Abstract: A ductile damage progress of an aluminum single crystal with the prior activity of the single slip system under tensile loading was verified by a profile analysis using white X-ray obtained in BL28B2 beam line of SPring-8. In this study, the aluminum single crystal of the purity 6N was used as a specimen prepared in I-type geometry for tensile test. A notch was introduced into one side of the center of a parallel part of the specimen by the wire electric discharge machining. White X-ray beam, which has 50 μm in both height and width, was incident into the specimen on the Bragg angle θ of 3 degrees using energy dispersive X-ray diffraction technique. The specimen was deformed by elongation in the direction of 45°to [11 and [11 crystal orientations, respectively, and a diffraction profile of the white X-ray from Al220 plane was analyzed. In profile analysis, an instrumental function was defined in consideration both of a divergence by a slit and a response function peculiar to the energy dispersive method. The Gauss component of integral breadth related to non-uniform strain and the Cauchy component of integral breadth related to crystallite size were determined by eliminating the broadening by the instrumental function from the diffraction profile of white X-ray. As a result, the characteristics of ductile damage progress near the notch of the aluminum single crystal were inspected from the distribution of both non-uniform strain and dislocation density.