Advanced Materials Research Vols. 26-28

Abstract: Cu-Be alloy (C17200) rod having diameter of 23.5mm was produced by a vacuum continuous casting method at furnace temperature range of from 1240°C to 1260°C with casting speed range of from 35mm/min to 103mm/min. When the furnace temperature was 1240°C and 1250°C, Cu-Be alloy rod without fracture could successfully produced at high casting speed of 103mm/min. However, when the furnace temperature was 1260°C, the breakout occurred at casting speed faster than 78mm/min. Surface roughness (Ra) increased with increasing not only a furnace temperature but also a casting speed.

Abstract: Fatigue strength of Al5083-O FSW joints was evaluated in the relation of the FSW conditions. Static strength of the joints in a range of FSW conditions was the same as that of base metal. Because the fracture of the joints occurred at the base metal in the tensile tests. Therefore the joint efficiency in tensile strength of joints with the FSW condition of tool rotation: 800 rpmwelding speed: 100 mm/min (800-100), 800-200 and 500-100 are all hundred percent. However, the fatigue strength of those joints with fine static strength varied very much. The joint efficiency for fatigue strength varies from 75% for 500-100 to 31% for 800-200. Crack path in fatigue test was always initiated at the center of back surface of FSW weld zone, and propagated through stir zone. Crack growth rate measurement and fracture surface analysis resulted the difference of the joint efficiency has a connection with the incomplete welding at back surface of joints.

Abstract: A static magnetic field and an alternating current are imposed on a metallic alloy during solidification for a crystal alignment of the primary phase. A Sn-10%Pb is selected as a sample because its primary phase is expected to have an anisotropic nature in magnetic susceptibility. In the x-ray diffraction pattern of the sample solidified without the magnetic field, the first and second highest peaks are (101) and (211) planes. On the other hand, those solidified with the magnetic field are (200) and (220) planes which are magnetically preferred planes. That is, the primary phase crystals in the sample solidified with the magnetic field are aligned to the specific direction.

Abstract: The effect of aging temperature and aging time on properties of Cu-3.2Ni-0.75Si-0.3Zn alloy were studied. The alloys were isochronally or isothermally aged after solution treatment. The cold rolling prior to the aging treatment was used to increase the precipitation rate .The microstructure of the alloy was studied by means of transmission electron microscope (TEM). The results show that the fine and dispersed precipitates are fully coherent with the Cu matrix and make the alloy possesses higher hardness and conductivity after the alloy was solution at 1173K and then aged at different time. The precipitates responsible for the age-hardening effect was Ni2Si.The transformation kinetics were studied by analyzing the electrical resistance variation of the solution Cu-3.2Ni-0.75Si-0.3Zn alloy in the process of aging.

Abstract: CaAl2O4:Eu2+ with high brightness and long persistent luminescence were prepared by solid state reaction method. The phosphor compositions with varying Eu2+ were investigated by powder X-ray diffractometer (XRD), SEM, TEM, photoluminescence excitation and emission spectra. Broad band UV excited luminescence of the CaAl2O4:Eu2+ was observed in the blue region (λmax = 440 nm) due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ ion. The particle size also plays a role deciding the luminescence characteristics of these phosphors. The decay time of the persistence indicated that the persistent luminescence phosphor has bright phosphorescence and maintains a long duration.

Abstract: The influences of hydrogen absorption on the Curie temperature TC and the isothermal magnetic entropy change for La0.5Pr0.5(Fe0.88Si0.12)13 have been investigated, because the magnetocaloric effects have been confirmed to be enhanced after a partial substitution of Pr for La in La(Fe0.88Si0.12)13. The value of TC for La0.5Pr0.5(Fe0.88Si0.12)13Hy increases from 185 to 324 K with increasing y from 0 to 1.6. The maximum value of the isothermal magnetic entropy change ,Sm MAX is slightly decreased by hydrogen absorption. However, ,Sm MAX = -26 J/kg K in a magnetic field change of 5 T for La0.5Pr0.5(Fe0.88Si0.12)13H1.6 is still larger than the value of -23 J / kg K for La(Fe0.88Si0.12)13H1.5 having almost the same value of TC. Consequently, ,Sm MAX of the La0.5Pr0.5(Fe0.88Si0.12)13Hy is larger than that of La(Fe0.88Si0.12)13Hy in a wide temperature range covering room temperature.

Abstract: The anodic aluminum oxide (AAO) templates were prepared by a two step anodization process in a mixture phosphoric acid, sulfuric acid and chromic acid and oxalic acid. The pore of anodic aluminum oxide templates were hexagonal arranged pore domains. Oredred Nickel nanowires were prepared in this porous anodic aluminum oxide templates from Watt solution and additives by an electrodeposition. The diameter of Nickel nanowires in the array were about 80 nm and the length is about 800 nm with the aspect ratio of about 10. The ordered Nickel nanowires were characterized by X-ray diffractometer, scanning electron microscopy and magnetometer.

Abstract: In this study, we have investigated a texture and microstructure of gold bonding wire by transmission electron microscope, X-ray diffraction and electron back scatter diffraction according to process parameters, such as casting, drawing and annealing processes. The gold was cast into 7mm diameter rods by vertical continuous casting technique, the cast rods were drawn to a final wire size of 25μm, and then the fine wires were annealed. A unidirectional solidification structure having <100> fiber texture of cast rod was strongly developed depending on casting route and speed. In the sample with unidirectional microstructure developed in partial it is found that dislocation substructure with nano-size appeared to display a characteristic feature, while no dislocation substructure is seen in the sample with complete unidirectional microstructure. Interface stability between solid and liquid may be responsible for this difference in dislocation substructure. With decreasing casting speed <100> fiber component became weak. Initial texture plays important role on development of <111> fiber texture at drawing and final annealing stages. On the basis of results obtained it is suggested that both the initial texture are important in controlling the texture of gold bonding wire.