Kiyotaka Katou

Porous Structure and Mechanical Properties of the Cellular Metallic Materials Fabricated by Sintering Al Powder Coated with Sn

The deposition of pure tin onto pure aluminum powder in its self-convective motion by magnetron DC sputtering was examined in order to prepare Al-Sn composite powder and thereby to improve the sintering of the aluminum particles, aiming at the development of highly structure-controlled porous aluminum materials. The fabrication of porous aluminum materials was carried out by space-holder method using the prepared Al-Sn composite powder in ordinary powder metallurgy processing. The effects of the sputterdeposition of tin on porous structure and mechanical properties of the sintered compact were investigated. It was found that the porous structure of the sintered porous materials with the porosity 80% was better regulated by the sputter-deposition, compared to that without the deposition. Regarding their compressive properties, it was found that the plateau stress of the sintered porous materials reached by the sputter-deposition twice as high as that without the deposition. Therefore it was concluded that coating of aluminum powder with tin deposits enables the porous-structure to be controlled more effectively in fabricating sintered highly porous aluminum materials, as well as improves their mechanical property.

Nondestructive Structural Analysis on Deformation Properties of Highly Porous Aluminum Material

The cell-structure of highly porous aluminum material prepared by melt foaming technology was investigated under deformation with fine-focus X-ray 3D-CT to make clear the development target porous material for automobile industries with improved reliability. It was confirmed that structures with more fine, more uniform and exclusion peculiar anisotropic pores would make improved mechanical properties of the material.

Compressive Properties and Energy Absorption of Hollow Sphere Aluminum

Manufactured cellular aluminums have been developed for a wide range of automotive applications where weight savings, improved safety, crashworthiness and comfort are required. The plateau deformation behavior of cellular aluminums under compressive loading makes this new class of lightweight materials suitable for energy absorption and comes close to ideal impact absorbers. In the present study, aluminum hollow hemispheres were firstly processed by pressing. Hollow sphere aluminum samples with a body-centered cubic (BCC) packing were then fabricated by bonding together single hollow spheres, which were prepared by adhering together hollow hemispheres. Hollow sphere aluminum samples with various kinds of sphere wall thicknesses of 0.1 mm, 0.3 mm and 0.5 mm but the same outside diameter of 4 mm were investigated by compressive tests. The effects of the sphere wall thickness on the mechanical properties and energy absorption characteristics were investigated.

Growth of Normal Human Osteoblast Cells on Hydroxyapatite/Titanium Alloy Composites Formed by Implantation of Hydroxyapatite Granules into Titanium Alloy

On the hydroxyapatite/titanium alloy composite disks, the normal human osteoblast cells were cultured. As a result, the samples were covered with normal human osteoblast cells after 2 hours. Moreover, we did not observe cracks in any of the HA granules, and the normal human osteoblast cells extended between the HA granules and the titanium alloy. From these results, we have concluded that this material has good biocompatibility.

Effect of Cu Addition on Microstructures for Ti(C,N)‐Mo2C‐Ni

The microstructural evolution of Ti(C,N)-Mo2C-Ni cermets with/without Cu were investigated. The microstructures of them were core-rim structures, regardless of Cu contents. Cu existed in Ni binder phase. In the case of lower Ni content, the contiguity of the hard phase for the cermets with/without Cu is same. On the contrary, in the case of higher Ni content, the contiguity of the hard phase for the cermets with Cu is lower than that without Cu.

Effect of Sintering Techniques on Mechanical Properties of WC‐FeAl Composites

In this paper, the authors represent the mechanical properties of WC-FeAl composite fabricated with two sintering techniques. The WC-FeAl composite often is obtained through liquid-phase sintering process by conventional vacuum sintering technique. Contrary, the use of pulse current sintering techniques enables to density the WC-FeAl composite at a temperature lower than that of FeAl liquid phase formation. That difference of sintering temperature results in crucial difference of the microstructure of the composites. Fine WC grains and small FeAl phases are observed in the composite fabricated from the pulse current sintering technique, whereas some WC grain growth and huge FeAl phases are observed from the sample of vacuum sintering technique. As a result, superior mechanical properties such as Vickers hardness and bending strength are obtained from the samples of the pulse current sintering technique in the WC-FeAl system.

Coating of Granular Polymeric Spacers with Copper by Sputter-Deposition for Enhancing Cell Wall Structure of Sintered Highly Porous Aluminum Materials

The deposition of copper onto acrylic resin powder in its self-convective motion by magnetron DC sputtering was examined in order to prepare granular polymeric spacers coated with the metal, aiming at enhancing the cell wall structure of sintered highly porous aluminum materials. The fabrication of sintered highly porous aluminum materials was carried out in an ordinary powder metallurgy processing combined with a space-holder method with the polymer-copper binary spacer granules prepared by powder-coating using the sputter-deposition technique. The effects of the sputter-deposition of copper onto the spherical polymeric spacers on cell structures of the sintered porous compacts were investigated. According to optical observations, it was found that the sputtered copper could be uniformly and adherently deposited onto the surface of the acrylic granules. According to EPMA analysis on the cross-section on a sintered porous compact, it was found that Cu atoms were distributed at the vicinity of its cell walls, concluding that cell wall structures could be enhanced by this processing. Therefore it was expected that the compressive properties of the sintered highly porous aluminum materials were also improved by this powder coating process.

Structural analysis on anisotropic deformation properties of highly porous aluminum material

The cell-structure of highly porous aluminum material prepared by foaming of aluminum alloy melt with titanium hydride was investigated nondestructively with fine-focus X-ray 3D-CT at several interrupt steps during slow compressive deformation. The foamed highly porous aluminum has anisotropic shape of each cell inevitably because of gravity force during solidification of foamed material and mechanical properties especially the dependence on the deformation direction of highly porous aluminum is analyzed well from the size and shape of each void composing the porous material. The statistic anisotropic distribution of these form factors such as three axial lengths and directions at the time of ellipsoidal approximation of each cell was found to be less important to improve the mechanical properties of this type of material.

Surface structure of Ti-O films formed on pure titanium by anodic oxidation

The formation of Ti-O thin films on pure titanium was carried out by anodic oxidation, not only to improve the corrosion resistance of the material but also to form stable coating in passive state with the adsorption site for the BMP(Bone Morphogenetic Protein) on the material, aiming at the clinical use of the material as a carrier or a substratum for the BMP. Furthermore the effects of electrolytic voltage ranging from 110V to 220V for the anodic oxidation on the formation of Ti-O films on the pure titanium were investigated by analysing the surface morphology, the layer composition and the structural property. The sparking voltage was about 160V on the pure titanium material. On the treatment below the sparking voltage, the Ti-O films formed by anodic oxidation was thin and optically interferential, while above the sparking voltage, thick Ti-O films having many pin-holes ranging from 0.1 to 0.3 micrometer in diameter as well as fine craters ranging from 2 to 3 micrometer in diameter were formed on the treated surface. According to Auger electron spectroscopy (AES) in-depth profiles, it was found that the Ti-O films formed above the sparking voltage was around 10 times thicker than those formed below the sparking voltage. On the basis of X-ray diffraction (XRD), it was concluded that the titanium oxide of anatase phase was formed in both the films formed by anodizing below and above the sparking voltage.

Improved adhesion of titanium oxide film to titanium-base alloy by Ti/O compositional gradient using reactive sputter-deposition

Abstract Deposition of titanium oxide film having Ti/O compositionally gradient layer onto titanium-based alloy such as Ti-6Al-4V was carried out by reactive DC sputtering, in order to improve not only the biocompatibility of the alloy but also the adhesion at the interface between the deposited titanium oxide film and the alloy substrate with preserving the high hardness and the passivity of the titanium oxide film. The effects of Ti/O compositional gradient on adhesion of the film at the interface to the alloy substrate were investigated by comparing the adhesion of Ti-O compositionally gradient films at the interface boundary with that of Ti-O compositionally constant films at the interface. The compositional gradient was realized by varying continuously the oxygen content in Ar-O 2 sputter gas mixture during the sputter-deposition. According to AES in-depth profiles, the oxygen(O) concentration in the deposited film decreased gradually in-depth direction from the surface toward the substrate, confirming that a film with Ti/O compositional gradient, i.e., a Ti-O compositionally gradient film had formed on the alloy substrate, and thereby expecting that the stress concentrated at the interface between the deposited film and the alloy substrate could be relaxed. On the basis of indentation-fracture tests, it was found the compositionally gradient film had more adhesion at the interface than the compositionally constant film, concluding that the Ti/O compositional gradient layer improved the adhesion of the deposited titanium oxide film.