Role of second-phase particles in chip breakability in aluminum alloys

To evaluate chip breakability, turning tests for various wrought aluminum (Al) alloys were carried out with a cemented carbide tool (K10) in dry and wet cutting conditions. In the alloys, Al₂Cu, Al₆Mn, Mg₂Si, Al–Fe–Si system compounds and eutectic Si were observed as second-phase particles. Chip breakability of the alloys containing Al₂Cu or Si were superior to those of those containing Mg₂Si or Al–Fe–Si. This tendency was more prominent in wet cutting than in dry cutting. The second-phase particles of Al₂Cu and Si in these alloys fractured during the machining process. It was estimated that the fractured second-phase particles acted as the cause of chip breaking. Moreover, the increase of the chip breakability in wet cutting was attributed to the Rehbinder effect due to the penetration of cutting oil into the micro-cracks.     

Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder

In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.     

Tensile test for estimation of thermal fatigue properties of solder alloys

A tensile test is proposed to evaluate the thermal fatigue resistance of solder alloys. The test is based on the strain rate change method to obtain the strain rate sensitivity index, m. The m value is obtained at various strains during the tensile test. The plots of m and strain where m is measured showed a linear relation; therefore, the m value at zero strain, m0, and the gradient, k, are obtained by extrapolation. The m value at zero strain related to the coarseness or fineness of solder alloy microstructure; m0 becomes lower with coarsening of the microstructure. The solder alloys with low m0 and low k have excellent thermal fatigue resistance when compared with alloys with high m0 and high k. m0 and k would be good measures to estimate the thermal fatigue properties of solder alloys; highly resistant alloys have low m0 and low k. This revised version was published online in November 2006 with corrections to the Cover Date.     

Component spatial pattern analysis of chemicals by use of two-dimensional electro-optic terahertz imaging

We demonstrate a method of chemical mapping by using the transillumination terahertz (THz) images obtained by two-dimensional electro-optic THz imaging. The images and spectral data were measured between 0.1 and 1.0 THz. An experimental sample consisting of three chemicals was prepared, with one in two concentrations. By introducing the component spatial pattern analysis based on the least-squares method, the chemical composition, spatial distribution, and difference in concentration were clearly determined.     

Growth factor receptor-bound protein 2 (Grb2) association with hemopoietic specific protein 1: linkage between Lck and Grb2

To analyze the growth factor receptor-bound protein 2 (Grb2) signaling pathway in lymphoid cells, we used expression cloning to isolate the genes encoding proteins that associate with Grb2. We find that the Src homology 3 domains of Grb2 directly associate, in vitro and in vivo, with murine hemopoietic specific protein 1 (HS1), a protein identical to Lck-binding protein 1. Because HS1 associates with the p56(lck) and p59(lyn) tyrosine kinases in vitro and in vivo, and becomes tyrosine phosphorylated upon various receptor stimulations, our present data suggest that HS1 mediates linkage between Lck or Lyn and Grb2 in lymphoid lineage cells.     

Functional monomers and polymers, 98. Asymmetric induction by chiral polymers containing bornyl groups

In order to determine the catalytic ability of the polymers containing chiral bornyl groups to the asymmetric induction, the asymmetric addition reaction of dodecanethiol to isopropenyl methyl ketone was studied using synthetic chiral polymers having pendant bornyl groups, in comparison with the case of using a monomeric model compound, i.e. d-bornyl acetate, and also poly(methyl methacrylate). It was found that the polymers having chiral borynl groups were effective for the asymmetric induction, and the optical yield depended on the bornyl group content in the polymers.     

ESR studies on the dimer formation between copper ions in the poly(vinylimidazole) · copper(II) complex

Summary ESR studies were made on the poly (vinylimidazole)· copper(II) complex in a lower magnetic field near 1600 gauss. The absorption in this region was observed for the poly(vinylimidazole) · copper (II) complex system while no absorption was present for the imidazole· copper (II) complex. The result was interpreted in terms of the dipolar interaction between copper (II) ions in the polymeric complex system, where the copper (II) ions were put together on the polymeric ligand in a highly condensed state.     

Non-ignition of an ejected flame through a gap greater than the quenching distance

When a gap is greater than the quenching distance, the flame from an explosion inside a chamber can pass through the gap, but it will not always ignite an outside combustible mixture. There is a non-ignition gap distance, greater than the quenching distance, below which ignition will not occur, and above which it will. The present paper presents experimental determinations of non-ignition gap distances for different values of several parameters (gap width, number of gaps, and chamber volume) for various rectangular gaps with a wide range of lengths. A rectangular gap has three dimensions. One of these is here referred to as the gap distance, the others being gap width and gap length; diagramme definitions of the terms are given. The gap distance for non-ignition varies with the values chosen for the other two dimensions. It increases as the gap width decreases. But when gap length is varied for gap widths over 4.0 cm, the non-ignition gap distance first increases with increasing gap length, and then levels off. A second increase may occur or not, depending on other parameters. In particular, any given sectional gap area (fixed values for gap width and gap distance) may be subdivided, giving rise to multi-layered gaps. Experiment establishes that such subdivision is available as a method of preventing ignition of an outside combustible mixture, since ignition may occur through a single gap of given area and not through a subdivided multi-layered gap of the same area. At multi-layered gaps, one gap flame is far in advance of the others. Other gap flames are either soon extinguished within the gap, or advance a short distance without emerging. It seems permissible to consider the resultant as one flame for analysis. The magnitude of the non-ignition gap distance for multi-layered gaps is proportional to ut, u being the ejection velocity of the flame from the gap, and t the time taken for the flame to pass from the jet origin to the gap exit.     

Effects of Co and Ni addition on reactive diffusion between Sn–3.5Ag solder and Cu during soldering and annealing

The reactive diffusion between Sn–Ag solders and Cu was experimentally examined during soldering and isothermal annealing. Three sorts of solders with compositions of Sn–3.5Ag, Sn–3.5Ag–0.1Ni and Sn–3.5Ag–0.1Co were used for the experiment. Each solder was soldered on a Cu plate at 523 K (250 °C) for 1–60 s in a pure nitrogen gas, and then the solder/Cu diffusion couple was isothermally annealed at 423 K (150 °C) for 168–1008 h. Due to soldering, only Cu₆Sn₅ is formed at the interface in each diffusion couple. On the other hand, Cu₃Sn is produced between Cu₆Sn₅ and Cu owing to the isothermal annealing. The composition of Cu₆Sn₅ is (Cu_0.8Ni_0.2)₆Sn₅ and (Cu_0.93Ni_0.07)₆Sn₅ on the solder and Cu₃Sn sides, respectively, in the (Sn–3.5Ag–0.1Ni)/Cu diffusion couple, and it is (Cu_0.9Co_0.1)₆Sn₅ and (Cu_0.99Co_0.01)₆Sn₅ on the solder and Cu₃Sn sides, respectively, in the (Sn–3.5Ag–0.1Co)/Cu diffusion couple. Different rate-controlling processes were suggested for the (Sn–3.5Ag)/Cu, (Sn–3.5Ag–0.1Ni)/Cu and (Sn–3.5Ag–0.1Co)/Cu diffusion couples. Finally, thermodynamic models were herein adopted to explore influences of the additives on the thermodynamic interaction of the component elements and the driving force for the growth of intermetallics.