Kazumi Minagawa

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.

Tensile behavior change depending on the microstructure of a Fe–Cu alloy produced from rapidly solidified powder

Abstract The relationship between consolidating temperature and the tensile behavior of iron alloy produced from Fe–Cu rapidly solidified powder is investigated. Fe–Cu powder fabricated by high-pressure water atomization was consolidated by heavy rolling at 873–1273 K. Microstructural changes were observed and tensile behavior was examined. Tensile behavior varies as the consolidating temperature changes, and these temperature-dependent differences depend on the morphology of the microstructure on the order of micrometers. The sample consolidated at 873 K shows a good strength/elongation balance because the powder microstructure and primary powder boundaries are maintained. The samples consolidated at the higher temperatures have a microstructure of recrystallized grains, and these recrystallized samples show the conventional relationship between tensile behavior and grain size in ordinal bulk materials.

Microstructural Valuation of Iron-Based Composite Materials as an Ecomaterial

One of an important method to realize is said that we should take recycle processes into consideration and select the material without the mixture of particular elements that make it difficult to recycle. Therefore, it is useful to control of microstructure for improvement. From this point of view, we paid attention to “SCIFER (that is made from Kobe Steel Ltd.)” that has a recyclable formation (Fe-C-Si-Mn) and superior characteristic (tensile strength is 5000MPa). The grain size of this fiber is nano-size. In this study, we used this material and compounded it together with iron-matrix to make an iron-based composite for recycle and investigated the possibilities of realization. The difficulty of this study is to make this composite without injuring the fibers microstructure. Therefore, we have adopted powder metallurgy which could fabricate composite at low temperature comparatively. Especially, Ultra Fine Particles (UFP) that would sinter at low temperature to bond the interface between fiber and matrix with keeping fibers capacity. This method is useful to ascend the density of the matrix. Results are as follows. (1) Utilization of UFP slurry made it possible to adhere UFP to the surface of fiber and seed powder. Still more, this procedure enabled it to make a thin film uniformly by selecting the condition of slurry density and procedure of dryness. (2) Applying UFP to the surface of fiber and seed powder make it possible to get the bond between fiber and matrix. By the bond of interface, both fracture strength and energies have ascended remarkably due to pull out of fiber.

Improvement in elongation of sintered Fe–Cu alloy by chemical reduction of the surface of rapidly solidified powder

Abstract The effect of oxide inclusions on the tensile properties of a Fe–Cu consolidated alloy was investigated. Fe–Cu powders with a copper content in the range of 0.5–5 mass% were prepared by high-pressure water atomization and reduced in a hydrogen atmosphere to remove surface oxides. The as-atomized and reduced powders were consolidated by groove rolling at 973 K. Microstructures were characterized by scanning electron microscopy and tensile properties were determined. The microstructure where recrystallized grains appeared was observed in the samples from both powders; there were fewer and smaller inclusions in the samples from the reduced powder. Reduction of the oxide inclusions contributed to increased elongation of the consolidated samples. Control of the inclusion at the powder surface is necessary in order to obtain plasticity.

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.

Preparation of Exfoliated Melamine Modified Mica/Polyamide-6 Nanocomposite and its Properties

The Expandable Mica was Modified with a Melamine Hydrochloride Salt at 60°C for Three Hours. the Resulting Melamine-Modified Mica (MME) was Melt-Kneaded with Polyamide 6 (PA6) Using a Twin-Screw Kneader at 250°C. the Addition of MME to the PA6 Matrix Resulted in a Finer Dispersion, as Evidenced by the Disappearance of the (001) Reflections in the XRD Patterns and TEM Image. the Tensile Modulus of MME/PA Nanocomposite (including 4.1 Mass % Mica) Increased by Approximately 1.8 Times Compared with that of the Neat PA6, which can be Attributed to the Increasing of the Exfoliated Silicate Platelets and the Dominating of the γ Crystalline Form in the Nanocomposites.

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.

Hybrid Atomization Method for Manufacturing Fine Spherical Metal Powder

Hybrid atomization is a new atomization technique that combines gas atomization with centrifugal atomization. This process can produce fine, spherical powders economically with a mean size of about 10 μm diameter and a tight size distribution. Experiments on the process were carried out using a Sn-9 mass% Zn alloy to investigate the influence of processing parameters on powder characteristics in hybrid atomization. The primary atomization mechanism under normal hybrid atomization conditions is predicted to be direct drop formation mode.

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.

EPMA Composition-coordinate Mapping Analysis of the Phase Change of Atomized Bi-Sr-Ca-Cu Oxide

A new method of EPMA mapping was developed and applied to the analysis of Bi-Sr-Ca-Cuoxide phases from atomized glass powder. The EPMA composition-coordinate mapping method, in which the frequency of the located spot-area of the same composition is plotted on thecoordinate with the concentration of each element, clearly showed the phase separationfrom homogeneous glass powder. A localized distribution of composition was found nearCa2CuOx with several percentage of Sr, and the distribution was connected with the mainphase. The main phase also had two spread of distribution to CuO and SrO. In the sampleconventionally mixed and sintered, Cu-rich phase without Bi was appeared instead of CuOand SrO.