Susumu Takamori

Production of fine spherical lead-free solder powders by hybrid atomization

Considerable R&D efforts in last decade have identified several promising lead-free tin alloys for the replacement of lead-containing solders in microelectronic applications. However, it is difficult or uneconomical to produce high-quality solder balls industrially by means of conventional atomization methods. To produce acceptable lead-free solder balls efficiently and industrially, a novel powder-making process change to active voice. Hybrid Atomization that combines free fall gas atomization and centrifugal atomization effectively, was invented and developed recently by us. This new technique can produce very fine, spherical tin alloy powders with mean diameters of about 10 mm, very narrow size distributions, few satellites and low production costs. Taking Sn-9mass%Zn alloy as an example, process experiments were carried out and the optimal processing conditions obtained. Results show that the influences of processing parameters and optimum conditions are very different from those in conventional atomization processes. The spherical powder with a mean particle size of 10.6 mm and a standard deviation of 1.3—1.7 mm was obtained in the determined optimum condition.

Flame retardancy of clay–sodium silicate composite coatings on wood for construction purposes

Composites of clay minerals mixed with sodium silicate as new inorganic flame retardants for wood have been investigated. Vermiculite beads were exfoliated by an ultra-sonication method and characterized by scanning electron microscopy, Fourier transform infrared absorption spectroscopy and thermogravimetry. The fire properties of wood samples coated with vermiculite and various vermiculite–sodium silicate composites were tested by a cone calorimeter. When the samples were exposed to the heat flux during the test, formation of a solid foamy layer was observed and composite coatings were effective in delaying of ignition coupled with decreasing the heat release rate and the total heat release. Synergy between the low thermal conductivity of the foamy layer and the release of water molecules from the composites improved the flame retardancy of these composite coatings. Among the coatings, multiple layers of sodium silicate and vermiculite exhibited the best flame retardancy in terms of maximum ignition time and minimum heat release rate.

The damping behavior of a Ni-50 at.%Ti shape memory alloy

In order to utilize the shape memory alloys (SMAs) for prospective damping applications, a near equiatomic NiTi alloy was investigated on a dynamic mechanical analyzer in the infrasonic frequency range. A high damping capacity stable to the variation of temperature can be obtained during a two-stage phase transformation and in the martensite state approaching to the martensite-parent phase transformation temperature in the NiTi SMA. The transient damping peaks associated with the phase transformation in the NiTi SMA shows a strong frequency dependence in both solutionized and annealed specimens. The frequency dependence parameter, n, was found to be in the range 0.3 – 0.6. For the applied strain amplitudes from 8.5 × 10 –6 to 5.0 × 10 –5 a clear strain amplitude dependence was not observed in the damping peaks, except for the solutionized specimens. While the damping capacity of the martensite state, characterized at 300 K, showed obvious frequency dependences in both the solutionized and annealed specimens, only the annealed specimens manifested the strain amplitude dependence. The different damping behavior was attributed to the internal structure of martensite, including dislocations, the twinning types and variant interfaces, changeable with the prior thermomechanical treatments.

Application of 3-Dimensional Powder Laminating Fabrication to Metallic Components

Production of dense metal products by a three-dimensional inkjet printing system was developed. Carbonyl nickel powder with a mean particle size of 5μm was used as a raw material and two binder supply methods, (i) coating a water soluble polymer on the powder and then supplying thin polymer-dissolved water from the inkjet head; (ii) supplying a binder directly from the inkjet head were examined. The layered green product was sintered in a hydrogen atmosphere at a temperature in the range of 1073-1623K. Microstructure observation was done and sintering procedure was discussed. Sintered samples fabricated from the coated powder had non-uniform microstructure with different densities due to agglomeration of the coated powder. The inhomogeneous microstructure was improved by screening the agglomerated particles, or agglomerating most of the powder to the contrary. However, the elimination of the density variegation was not achieved in the method using the coated powder. In samples made from the powder bonded by the binder directly, microstructure was fairly homogeneous. The homogeneous microstructure helped uniform sintering, and the macroscopic shape was retained after high temperature sintering at 1623K, and a high density of over 90% was achieved.

Refinement of Fe-Intermetallic Compounds by Caliber Rolling Process of AL-MG-SI-FE Alloys

The recycling process of aluminum scraps commonly contains high amount of impurities, especially Fe content which results in degraded properties compared with the primary aluminum production. The refinement of Fe-intermetallic compounds becomes increasingly important to extend the utilization of recycled aluminum. In this study, a thermo-mechanical process of Al-(2.2–2.3)mass%Si-0.9mass%Mg-(1.0–2.0)mass%Fe alloys by caliber rolling process was performed to investigate the refinement of Fe-intermetallic compounds and the mechanical properties. Fine fragmented Fe-intermetallic particles from around 200nm were achieved after 95% caliber rolling. The caliber rolling can effectively improve mechanical properties with good ultimate strength of 345–360MPa and high elongation of 15–25% in comparison with the as-cast l%Fe specimen with low ultimate strength of 269MPa and low elongation of 1.5%.

Evaluation of Damping Property of Aluminum-Alloyed Cast Iron by Several Methods

In this research, the effect of the aluminum addition to cast iron on damping property was investigated by central vibration method, dynamic mechanical analysis, ultrasonic attenuation measurement and impact sound method. All measurement results indicated that the addition of aluminum improve the damping property of cast iron.

Fabrication of Nano-Laminar Glass/Metal Composites by Sintering Glass Flakes

Fabrication of nano-laminar ceramic composite by a simple sintering technique was examined. Glass flakes with a thickness of 0.7μm coated with silver were used as model materials, and were consolidated by pulsed current sintering with a uniaxial press of 7.1MPa or 30MPa. By sintering the flakes at 943K, we obtained a fairly dense composite where the flakes were aligned by uniaxial press. The silver coating remained on the flakes through the sintering, and an interface layer between the flakes was formed. The sample’s indentation test demonstrated its high resistance to crack propagation through the transverse direction of the lamellar; this result was attributed to crack deflection at the interface and the accumulation of microfractures around the indentation mark.