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Titanium has widely been used as a biomaterial because of its excellent biocompatibility. However, problems with respect to biological reaction and fitness of elastic modulus for human bone have yet to be solved. Porous titanium is expected to be a promising material to solve these problems. The aim of this study is to clarify the effect of the porous titanium with and without annealing on the biomechanical compatibility. Porous titanium was made by spark plasma sintering. And the parts of the samples were annealed. The samples were machined from the sintered compacts for the evaluation of the mechanical properties. The tensile strength of porous titanium was 42 MPa, which is lower than half the value for human cortical bone, while the annealed samples was 95 MPa, a value somewhat close to that of the human cortical bone. We found that the mechanical properties with annealing porous titanium indicated a value close to the human bone.

In order to improve wear properties of austenite stainless steel, we applied powder composite process to obtain thick hard layer on stainless steel. The raw alloy powder was prepared by planetary ball milled tungsten carbide (WC) powder and SUS316L stainless steel powder. Sintering process was performed by pulsed current sintering (PCS) method. Wear properties were evaluated by pin-on-disk wear testing machine, and a remarkable improvement was confirmed in wear resistance property. In this investigation, we applied micro-sized testing technique to evaluate mechanical properties of WC layer and Stainless interface of layer. Micro-sized cantilever specimens with a size of 10×20×50μm3 were prepared by focused ion beam machining system. Micro-sized bending tests were successfully completed using a mechanical testing machine for micro-sized specimens. The maximum bending stresses were different for stainless matrix, interface layer, and SUS/WC composite. Ductile rapture surface was observed at stainless matrix, and brittle rapture surfaces at interface of WC layer and Stainless layer and SUS/WC composite layer.

Spherical submicron copper particles were synthesized through evaporation and subsequent condensation of copper powders in Ar-H2 thermal plasma. Copper powders of ∼40μm in size injected into the plasma, evaporated instantly and fine particles were formed through homogeneous nucleation and subsequent heterogeneous condensation. Particle size and the distribution in the synthesized powders were changed depending on the powder feed rate. Formation of submicron size spherical powders attributed to a significantly high degree of supersaturation in a vapor phase. Particle sizes of the as-produced powders range from submicron to several tens of micrometers. A simple sedimentation treatment was successfully applied to separate the as-formed powders with alcohol solvent to give uniform spherical submicron-size particles with monomodal size distributions. Cu-W composite powders were synthesized through the Ar-H2 plasma treatment of Cu-WO3 composite powders. The starting temperature of shrinkage was made significantly higher than pure Cu powders by mixing with several wt% of W.

The influence of the internal current for the ZnO ceramics on the sintering behavior by pulse current sintering (PCS) method was investigated. The electric resistance of the sintering ZnO ceramics drastically decreases by the addition of the small Al2O3, and it is expected that a part of sintering current flows in the specimen and affects the sintering behavior of the ZnO ceramics on the PCS method. To clear the dependence of inner current on the sintering behavior of ZnO ceramics, direct measurement of electric resistance of ZnO specimen under sintering by SPS device was carried out. It was observed that electric resistance of specimen decreases with increase in the temperature. The electric resistance begins to decrease from the low temperature of 200°C. The internal structure of sintered ZnO ceramics changed by the control of the internal current in the specimen using Al2O3 plate.

Carbon fiber/metal matrix composites were fabricated by powder metallurgy process, spark plasma sintering followed by rotary swaging, to achieve high heat conduction and low thermal expansion. Pitch-based carbon shortfiber was mixed with the powder of aluminum or copper. A volume fraction of the fiber was 40%. Orientation angles of the fiber to the compacting direction were measured in the longitudinal sections of the composites. Hermans' orientation parameter was adopted to evaluate the fiber orientation. The swaging process caused the parameter to change markedly from -0.9 to 0.9 in both of Al and Cu matrix composites. These values mean that the fiber is dispersed perpendicularly to the compacting direction in the sintered objects and dispersed in parallel to that one in the objects with swaging process. Thermal conductivity of the composites increases with increasing Hermans' orientation parameter. The thermal conductivity of Al and Cu composites was 210 and 420 W⋅m-1⋅K-1 at room temperature, respectively. Coefficients of thermal expansion of both Al and Cu matrix composites decreased approximately 25% as compared with those of monolithic Al and Cu metals.

The MA-SPS (mechanical alloying followed by spark plasma sintering) process was adopted to further improve the high temperature properties of a newly developed 36Cr white cast iron (a eutectic Fe-36Cr-9Ni-5Mo-0.45Si-2.2C alloy). α-Al2O3 powder with a mean diameter of 0.4μm was used as reinforcement for the MA material, and the volume fractions of Al2O3 in the composites were 10% and 30%. The results show that the microstructures of the MA materials were greatly refined compared to those of the conventionally solidified ingot and that their high temperature hardness and high temperature abrasive resistance were considerably improved. Also found was that the increase in the volume fraction of the Al2O3 powder increased both the hardness and the abrasive resistance of the composite materials.

Metal injection molding (MIM) process is hoped to be quite useful for improvement of the quality and productivity in the automotive sintered parts. In our previous studies, high performance ferrous sliding abrasive wear-resistant materials using prealloyed steel (SCM440) and 3mass%TiN powders were obtained by MIM process.This study has been investigated to develop the high performance self-lubricating wear-resistant materials in the same way. A water atomized tool steel (SKD11) powder was used as the matrix and 2-8mass% CaF2 powder was added to improve the self-lubricating properties. The compacts were densified to near full density by liquid phase sintering at 1493K, and the final carbon content was controlled to be almost 1.6mass%. CaF2 powder particles were distributed uniformly in the compacts. Addition of 6mass% CaF2 powder caused a remarkable improvement of wear-resistance under non-lubricating conditions. This indicates that MIM process has enormous potential to produce high performance ferrous composites for the automotive sintered parts.

For miniaturization and complication of the shape of electronic devices in recent years, both high magnetic and mechanical properties are also being required to the soft magnetic components. A metal injection molding(MIM) process has the attributes of forming the high density, complex shaped and high performance components, which seems to be a suitables process for fabricating the higher performance soft magnetic components.In this paper, the effect of MIM process conditions on the magnetic and mechanical properties of soft magnetic materials such as Fe-Ni and Fe-Si alloys were investigated. Although the final density was obtained approximately 96% of theoretical in both steels, the magnetic properties were similar or inferior to that of the pure iron. Especially, the coercive force was increased with an addition of alloying elements, because the orientation of domain walls were prevented from the grain refining and the residual oxides. Generally, taking account of the improvement in the mechanical properties which are superior to that of the conventional P/M materials, it will be able to apply a MIM process to the soft magnetic components.

Metal injection molding (MIM) is a suitable processing route for the mass production of complex-shaped and high performance components. Therefore, MIM process is hoped to be quite useful for improvement of the quality and productivity in the automotive sintered parts.This study has been performed to develop the high performance ferrous sliding abrasive wear-resistant materials through MIM process. A prealloyed powder (SCM440) was used as the matrix and also 3mass%TiN powder was added to improve the wear-resistance. Those compacts were densified to about 95% of relative by sintering, and the final carbon content was almost exactly controlled to be 0.4mass% by adjusting the debinding and sintering atmospheres and conditions. Sintered compacts showed the dual homogeneous microstructures consisted of ferrite and fine pearlite, and the pores and TiN powder particles were distributed uniformly, regardless of the injecting direction. Thus, the wear characteristics were not influenced by the injecting direction. Injection molded SCM440 steel showed the same wear-resistance as the wrought SCM440 steel. However, addition of 3mass%TiN powder caused a remarkable improvement of wear-resistance, which indicate that MIM process has enormous potential to produce high performance ferrous composites for the automotive parts.