Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publisher：Japan Society of Powder and Powder Metallurgy  

<p>Anisotropic shrinkage of powder compacts is often observed in sintering process. Although controlling the shape and size of the sintered body is important to reduce manufacturing cost, it is difficult to understand the factors affecting anisotropic behavior only by experimental observation. In the present study, two-dimensional numerical simulation for sintering process of elliptical particles is performed with changing particle alignment and orientation by using a combined phase-field method (PFM) and discrete element method (DEM). The effects of the size of inter-particle contact plane, the sintering force, and the pore configuration on sintering anisotropy are examined. According to the calculated results, anisotropic shrinkage appears depending on the particle arrangement. The elliptical particles oriented horizontally enhance the horizontal shrinkage. The inter-particle contact in vertical direction reduces the vertical shrinkage. The shrinkage behavior of compacts of elliptical particles can be basically explained by considering the combination of the sintering stress and the size of inter-particle contact plane, except the case of arrangement with largely elongated pore structure.</p>

DOI： 10.2497/jjspm.24-00011

CiNii Research

Language：Japanese   Publisher：Japan Society of Powder and Powder Metallurgy  

<p>Since Ti alloys are difficult-to-machine materials, the application of powder metallurgy such as metal injection molding (MIM) is desired. Although injection molded Ti-6Al-4V alloys showed sufficient tensile properties, their fatigue strength was significantly lower than that of the wrought material. In this study, various approaches were applied to improve the fatigue strength through MIM processing parameters such as raw material powders, addition of 4th and 5th elements such as Mo and B, sintering techniques, and heat treatment conditions. Eventually, we obtained the fatigue strength as same as wrought materials. We also investigated the factors, which control the fatigue strength of injection molded Ti alloys. Regarding the relationship between the pore size and grain size on the fatigue strength, it was found that the crack initiation occurred from the largest pore when the ratio of the pore size to the grain size was large, and simultaneously the fatigue strength was significantly decreased.</p>

DOI： 10.2497/jjspm.70.319

Scopus

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

Repository Public URL： https://hdl.handle.net/2324/7171755

Language：English   Publishing type：Research paper (international conference proceedings)  

Publisher：World PM 2022 Congress Proceedings  

To establish a quantitative relationship between fabrication parameters, pore-configuration, and mechanical properties in porous materials, the pore configurations were visualized by X-ray computed tomography (CT) about pure Ti-AM specimens fabricated under different laser beam conditions. Radius and sphericity of all pores were obtained by image analysis. Furthermore, using the 0th persistent homology, the pore configurations were qualified by the pair of birth and death values, b and d for all pores: |b| means a pore radius and d correspond to a half distance between adjacent pores. The significant correlations were confirmed between tensile strength/elongation and the parameters: the maximum value of |b|, the ratio of the mean values of |b| and d (neck geometry), and the sphericity of the largest pore. These were proposed as useful structural parameters representing 3D pore-structure in porous materials.

Scopus

Language：English   Publishing type：Research paper (other academic)  

We propose a new three-dimensional (3D) printing system for magnetic elastomer, which is composed of photo curable resin dispersed with magnetic particles. The obtained structure is magnetic and flexible so that they can work as an actuator by changing the applied magnetic field. During the curing process, a magnetic field is applied to set magnetic anisotropy at the curing portion, and we can design the motion of the actuator using this anisotropy. It means that we can not only print the 3D-structure but also print the deformation of printed actuator.

Language：English   Publishing type：Research paper (scientific journal)  

The purpose of this study was to explicate the mechanism of transition storage modulus and loss modulus under external magnetic field. Magneto-rheological elastomer (MRE) is expected to be used as damping material and actuator controlled by an external magnetic field. However, magnetic particles' behavior inside of MRE has not been explained completely. Especially, the mechanisms of loss modulus transition under external magnetic field has not been known well. We constructed a simple model with two magnetic particles, and try to make MRE behavior clear. In this report, we show a data of the viscoelastic property of MRE which consists of magnetic particles and polydimethylsiloxane (PDMS). The obtained viscoelastic property is explained by using two magnetic particles model.

DOI： 10.1541/ieejsmas.138.48

Language：English   Publishing type：Research paper (other academic)  

Although titanium alloy compacts manufactured by metal injection molding (MIM) process have the same static mechanical properties as that of wrought materials with similar composition, their fatigue strength shows remarkably lower levels. In this study, improvement of the fatigue strength of injection molded Ti-6Al-4V alloy compacts was performed by refining the pore and grain sizes through different approaches such as the usage of fine powders, dual phase region sintering, and hydrogenation and dehydrogenation treatment. Especially, the effects of pore size and grain size on the fatigue strength were evaluated. Essentially, the relationship between the fatigue strength and the grain size for HIP treated compacts obeyed the Hall-Petch law. On the other hand, for the injection molded compacts with pores, it was found that the largest pore dominates the fatigue strength in the case of the large pore diameter ratio to the grain diameter, while the relative density influences on the fatigue strength when the pore diameter ratio is small.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Analytical Study of Size Effects on Sintering Deformation of Ceramic Plates

DOI： 10.1299/jsmekyushu.2018.71.G12

Language：Japanese   Publishing type：Research paper (scientific journal)  

Development of Magnetic Drive Actuator Fabricated by 3D Printing System for Magnetically Anisotropy

DOI： 10.1299/jsmekyushu.2018.71.G24

Language：Japanese   Publishing type：Research paper (scientific journal)  

Design of 3-dimensional cilia motion by external magnetic field driven artificial cilia

DOI： 10.1299/jsmekyushu.2018.71.G23

Language：Japanese   Publishing type：Research paper (scientific journal)  

Sintering analysis of micro compacts with inhomogeneous powder packing structures

DOI： 10.1299/jsmekyushu.2018.71.G22

Language：Japanese   Publishing type：Research paper (scientific journal)  

Deposition patterning for solidification of ceramic powder at room temperature by laser shock wave

DOI： 10.1299/jsmekyushu.2018.71.G16

Language：Japanese   Publishing type：Research paper (scientific journal)  

Effects of differential speed rolling on orientation behavior of ceramic plate-like particles.

DOI： 10.1299/jsmekyushu.2018.71.G11

Language：English   Publishing type：Research paper (scientific journal)  

Artificial cilia actuated by an applied magnetic field have been developed. In our previous report, we demonstrated actuated cilia of a few millimeters scale, which were fabricated by cutting a magnetic elastomer sheet. The fabricated artificial cilia worked similarly to natural cilia; however, they had a much larger structure than natural ones, and showed difficulty for use in pumping systems in micro-total analysis systems (μTAS) fields. Thus, our goal is further miniaturization. In this study, we introduce a new process of fabricating smaller pillar structures with a magnetic orientation in each pillar by ultraviolet (UV) laser machining. We also give different orientations to groups of pillars by the alternate laser machining of the mold and casting processes.

DOI： 10.7567/JJAP.56.06GN15

Language：English   Publishing type：Research paper (scientific journal)  

Solid oxide fuel cells (SOFCs) are fuel cells made of ceramics. To increase the SOFC energy density, we developed an SOFC with a wavy electrolyte layer. As a wavy electrolyte has a larger reaction surface area than a flat electrolyte, a higher energy density could be obtained. Our proposed process is named micro-powder imprint (μPI) with a multilayer imprint process that is useful for fabricating a microscale pattern on a ceramic sheet such as an SOFC electrolyte layer. μPI is based on nanoimprint lithography; therefore, it also exhibits the same advantages of high resolution and mass productivity. The starting material for μPI is a compound sheet containing ceramic powder and binder materials consisting of thermoplastic resin. In this study, two different sheets were stacked into one sheet as a multilayer sheet for the μPI process to form a wavy compound sheet. As the initial state of the stacked sheet, including the mechanical properties of each layer, affects the final wavy shape, we changed the material composition. As a result, the SOFCs unit cell with a wavy electrolyte was fabricated. Note that the anode layer was formed at the same time. After adding the cathode layer, we succeeded in preparing a complete cell for testing power generation.

DOI： 10.7567/JJAP.56.06GL04

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, we report on a new system of three-dimensional (3D) printing for a magnetic elastomer that contains magnetic particles. Not only can we fabricate a three-dimensional structure, but we can also control the magnetically anisotropic property of each position in the structure using the present technique. Our new system employed photocurable poly(dimethylsiloxane) (PDMS) as the base material so that a method similar to a conventional 3D printing process with photolithography can be used. A magnetic powder was mixed with photocurable PDMS, and particle chain clusters were obtained by applying a magnetic field during the curing process. These chain clusters provide an anisotropic property in each part of the printed structure. We show some results of preliminary experiments and 3D printed samples in this paper. If the fabricated structure was placed under an applied magnetic field, each chain cluster will cause the rotational moment to be along the magnetic flux line, which can deform a soft matrix body. This deformation can be used as a magnetic actuator for the structure. Variable deformable structures could be developed using the present method.

DOI： 10.7567/JJAP.55.06GP18

Language：English   Publishing type：Research paper (scientific journal)  

In this paper, a biomimetic microstructure related to cilia, which are effective fluidic and conveying systems in nature, is described. Authors have already reported that a magnetic elastomer pillar actuated by a rotating magnetic field can work like a natural cilium. In the present work, we show examples of a cilia array with a metachronal wave as the next step. A metachronal wave is a sequential action of a number of cilia. It is theoretically known that a metachronal wave gives a higher fluidic efficiency; however, there has been no report on a metachronal wave by artificial cilia. We prepared magnetic elastomer pillars that contain chainlike clusters of magnetic particles. The orientation of chains was set to be different in each pillar so that each pillar will deform with a different phase.

DOI： 10.7567/JJAP.55.06GP19

Language：English   Publishing type：Research paper (scientific journal)  

As Ni-based superalloy has poor workability, direct laser forming (DLF) would be a powerful tool for fabricating the complex shaped Ni-based superalloy parts. We focused on the microstructure of the parts produced by DLF, the crystal grains of which grow along the building direction. This anisotropic microstructure is one of the major features of the parts produced by DLF, and which may cause anisotropic mechanical properties. In this work, the optimum laser-forming conditions such as laser power, laser scan speed, and powder feeding rate were determined by evaluating the density of the produced parts. Three types of tensile test pieces and two types of fatigue test pieces were fabricated in different building direction. They had higher ultimate tensile strength than that of JIS standards in wrought materials. However, their elongation was lower than that of JIS standards, and also the dispersion of elongation was large. On the other hand, fatigue limit was a little lower than the standard value. It was confirmed that the mechanical properties of Ni-based superalloy parts produced by DLF were different by a difference in building direction.

DOI： 10.2497/jjspm.63.427

Language：English   Publishing type：Research paper (scientific journal)  

Micro channels made of polymers are commonly used for MEMS and μTAS (micro-total analysis system) devices. In this research, we developed a process for fabricating a ceramic sheet with micro channels. The developed process is based on powder metallurgy process. A compound material, a mixture of ceramic powder and polymer, was prepared as sheet material. We employed laser machining to machine the sacrificial layer to form micro channels inside the sheet. We also employed imprinting, which is a process of pressing with a mould while heating, to form a structure with surface patterns and micro channels curving along with it. After the imprinted sheet was debound and sintered by heating, a ceramic sheet with micro-surface patterns and micro channels was obtained. As ceramics have high heat durability and low chemical reactivity, ceramic micro channels can be used for flow sensors or chemical reaction testers operated in harsh environments, such as high temperature or mechanical parts operated with reactive chemicals. In addition, by imprinting wavy patterns, the surface area can be increased. Therefore high efficiency heat exchangers can be built. Moreover, this method can be applied on SOFCs (solid oxide fuel cell) by fabricating YSZ (yttria stabilized zirconia) micro channels.

DOI： 10.2497/jjspm.63.511

Language：English   Publishing type：Research paper (scientific journal)  

Titanium alloys show not only the excellent mechanical properties but also good biocompatibility. However, they show normally poor machinability, which become the disadvantage of high processing cost. Metal injection molding (MIM) process is one of the techniques to improve that drawback. Because MIM process can produce the three dimensional complex shaped parts at low cost. Ti-6Al-4V is a typical titanium alloy and the MIM compacts show high static strength as same as wrought materials. However, their fatigue strength is a little low level as compared to wrought materials. To improve the mechanical properties of Ti-6Al-4V alloy compacts, it is important to refine the grain size and increase the relative density. In this study, the effects of the particle size of the powders on the mechanical properties were investigated. The use of a fine powder improved the mechanical properties because of their high density. Moreover, the crystal grain growth was restrained as compared to the case of the same relative density using larger powder.

DOI： 10.2497/jjspm.63.445

Language：English   Publishing type：Research paper (scientific journal)  

It is not easy to fabricate the complicate shaped titanium aluminide (Ti-Al) components by conventional methods such as machining or forging, and casting leads to inhomogeneous microstructures. Metal injection molding (MIM) has the potential to be a cost-efficient process and near net shape technique, especially for the complex shaped mass-produced components. In this study, Ti-Al intermetallic alloy compacts were fabricated through MIM technique. Sound compacts with over 95 % of relative density and without any warpage or defects were obtained thorough MIM process. Different microstructures of duplex, near lamellar, and full lamellar were obtained by changing the sintering temperature. Their tensile strength at room and high temperature is 85 to 90 % of that of wrought material. Tensile strength of MIM compact would be expected the same level with cast materials by optimization of sintering conditions, densification by HIP treatment and so on.

DOI： 10.2497/jjspm.63.457

Language：English   Publishing type：Research paper (scientific journal)  

Ti-6Al-4V alloy has attracted a lot of attention from the automotive and aerospace industries because of their outstanding specific strength and corrosion resistance. On the other hand, Ti-6Al-4V alloy has normally poor workability because of the low thermal conductivity and the low elastic modulus. Metal injection molding (MIM) process is expected to manufacture a complex part with near net shape and reduce the manufacturing cost. However, Ti-6Al-4V alloy compacts by MIM process had a problem of low fatigue strength compared to wrought material. In this study, we tried to add a minor amount of boron using TiB2 powder for improving the fatigue strength. Addition of boron resulted refinement of the grain size of lamellar structure, which lead to increase the high cycle fatigue strength and fatigue limit. In addition, tensile properties at high temperature was investigated.

DOI： 10.2497/jjspm.63.451

Language：English   Publishing type：Research paper (scientific journal)  

Yttria-stabilized zirconia (YSZ) has been used for an electrolyte of solid oxide fuel cells (SOFC). To enhance the efficiency of SOFC, we developed a corrugated, or wavy-shaped, YSZ sheet for the electrolyte. As the corrugated sheet has larger surface area than a flat-type sheet, higher energy density can be obtained. We have proposed micro powder imprint (μPI) with multi-layer imprint process to fabricate micro scale pattern on the both surfaces of a thin YSZ sheet. The μPI is a combined process of nano imprint lithography and powder metallurgy; the resolution is high, and the process is mass-productive. In this work, we selected a compound material containing YSZ powder and a binder consisting of thermoplastic resin as a starting material. The compound sheet was prepared by tape casting from slurry and was imprinted by a fine-patterned mold with stacked on a silicone rubber sheet. The silicone rubber was so flexible that micro patterns on the both sides of the compound sheet was obtained after imprint. In the present work, the process condition of μPI and the heat program of debinding and sintering were also considered. As a result, a wave-type sintered YSZ sheet without significant defects was successfully obtained.

DOI： 10.2497/jjspm.63.519

Language：English   Publishing type：Research paper (scientific journal)  

Metal Injection Molding (MIM) is an effective way to manufacture small components with low cost and high precision. However, in the case of large components, it becomes difficult to control the distortion and cracking because of the big shrinkage during debinding and sintering process. Therefore it is important to optimize the condition of each process to reduce the distortion of MIM compacts. Moreover, powder size is also one of the most important parameters. The small particle powder shows high shrinkage and high density as compared to large particle powder during sintering process. In this study, blending of both powders was conducted and the influence of powder size distribution on the distortion of complex shaped parts was evaluated. A coordinate measuring machine, which is a 3D device for measuring the physical geometrical characteristics of an object, was used to measure the distortion. Finally, through controlling the distribution of particle size, distortion of the comparatively large and complex shaped MIM compacts was successfully restrained.

DOI： 10.2497/jjspm.63.473

Language：Japanese   Publishing type：Research paper (scientific journal)  

Mechanical properties of MIM super high strengthening sintered low alloy steels with fine heterogeneous

DOI： 10.1299/jsmemecj.2016.S0410205

Language：Japanese   Publishing type：Research paper (scientific journal)  

Deformation Control of Large Sized MIM Parts

DOI： 10.1299/jsmemecj.2016.S0410101

Language：Japanese   Publishing type：Research paper (scientific journal)  

4-dimensional Printing Process Using Elastomer Dispersed with Magnetic Particles

DOI： 10.1299/jsmemecj.2016.S0440104

Language：Japanese   Publishing type：Research paper (scientific journal)  

Visco-elastic control of elastomer with magnetic particles by applied magnetic field

DOI： 10.1299/jsmemecj.2016.J2230204

Language：Japanese   Publishing type：Research paper (scientific journal)  

Surface Patterning on Ceramic Sheet by Microimprinting Process

DOI： 10.1299/jsmemecj.2016.S0410206

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

In recent years, the soft magnetic material parts have been widely used in the fields of industrial equipments, consumer electronics, automobiles, and so on. To fabricate these soft magnetic material parts, electrical steel and P/M method is normaly used. With the increase of fabricating complex shaped parts, processing method with more flexibility in design also be needed. For this reason, MIM process is hoped to be a near-net-shape, cost reduction and mass production method which can fabricate three-dimensional complex shaped parts. Fe-Cr-based soft magnetic material is developed in 1960s∼1970s to be used in corrosive environments. Because it is less expensive than the PB permalloy. Mainly composition comprising a 13 %Cr or higher is used to make material stable. However, the maximum magnetic flux density of material decreases with increase of Cr content. In this research, the effect of Cr content on the magnetic properties under DC and AC magnetic field were investigated by mixing SUS430L alloy powder and iron powder.

DOI： 10.2497/jjspm.62.431

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

This study aims to improve the fatigue strength of P/M gears and to substitute P/M gears for conventional wrought steel gears with reduced manufacturing costs. The 4600 series sintered alloy steels with mixed elemental powders show the mezzo-heterogeneous microstructure which consists of high-hard Ni rich areas and the surrounding martensitic structures. This mezzo-heterogeneous structure causes high strength to the products. In this paper, we discuss the effects of Ni contents on the contact fatigue strength, and the effect of the pore size is also discussed for further strengthening. Especially, from the evaluation of the area of isolated pores in the densified surface layer after the rolling, it was found that the decrease of pore sizes is very important to improve the contact fatigue strength.

DOI： 10.2497/jjspm.59.258

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Surface rolling were carried out using P/M spur gears of 0.6Mo-0.2C partially alloyed sintered steel with the density of 7.18 g/cm
³
. A CNC form rolling machine of axis intersection type was employed, and an unmodified screw-shaped rolling tool was prepared. Then, porosity distributions in the surface layer of rolled gear teeth root were measured and the effects of the surface rolling on the selective surface densification behaviors were evaluated. Moreover, to obtain higher fatigue strength, reverse rolling was introduced to standard gears. As a result, the porosities in the tooth root were sufficiently reduced at 700/μm feed in rolling process. Furthermore, a profile shifted gear was prepared to increase the effect of surface rolling. After case hardening, the single tooth bending fatigue durability reached to about 83% of the case hardened wrought steel gears of SCM415.

DOI： 10.2497/jjspm.58.692

Language：English   Publishing type：Research paper (scientific journal)  

This study aims at reducing costs of high load gear manufacturing, and substituting P/M gears for conventional wrought steel gears. In order to improve the fatigue strength of P/M gears, we focused on the rolling and the high performance sintered and heat treated 4600 series alloy steels with mezzo-heterogeneous microstructure which were made from the mixed elemental powders. The fatigue strength was determined by single tooth root bending fatigue test machine, and the effect of mezzo-heterogeneous microstructure and rolling on the fatigue strength was mainly investigated. The endurance limit at N=3.0× 10⁶ of the 500 μn rolled 6%Ni alloy steel gear compact showed 950 MPa which value is about 2/3 of the case hardened wrought steel (SCM415) gears. However, the endurance limit of rolled and heat treated gear compact showed lower value (630 MPa) as compared to as-rolled gear compact. This seems to be due to the decreasing the compressive residual stress by heat treatment and unfavorable mezzo-heterogeneous microstructures.

DOI： 10.2497/jjspm.58.350

Language：English   Publishing type：Research paper (international conference proceedings)  

Event date： 2023.6

Language：Japanese  

Country：Japan  

Event date： 2023.6

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Country：Japan  

Event date： 2023.6

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Country：Japan  

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Country：Japan  

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Event date： 2021.6

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Event date： 2020.6

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.10

Language：English  

Country：Japan  

Event date： 2019.9 - 2019.6

Language：Japanese  

Country：Japan  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2019.6

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

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Event date： 2019.6

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Event date： 2019.6

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Event date： 2019.6

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Event date： 2019.6

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Event date： 2019.6

Language：English  

Country：United States  

Event date： 2019.6

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Event date： 2019.6

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Event date： 2019.6

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Country：Japan  

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Country：Japan  

Event date： 2019.6

Language：Japanese  

Country：Japan  

Event date： 2018.11

Language：Japanese  

Country：Japan  

Event date： 2018.9

Language：Japanese   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2018.7

Language：Japanese  

Country：Japan  

Event date： 2018.6

Language：English   Presentation type：Oral presentation (general)  

Venue：San Antonio, USA.   Country：United States  

Event date： 2018.6

Language：Japanese  

Country：Japan  

Event date： 2017.8

Language：Japanese  

Country：Japan  

Event date： 2017.6 - 2019.6

Language：Japanese  

Country：Japan  

Event date： 2017.5 - 2017.6

Language：Japanese  

Country：Japan  

Event date： 2016.10

Language：English  

Venue：Hamburg   Country：Germany  

Metal Injection Molding (MIM) process is suitable for fabricating small parts in large quantity. In this work, relatively large and complex shaped parts were prepared thorough MIM. In order to decrease the deformation of sintered parts, powders of different sizes were mixed. The effect of powder particle distribution and powder loading on the distortion of complex shaped compacts were investigated and evaluated. Smaller deformation of thelarge and complex shaped parts could be realized by using mixed powder with smallerparticle.

Event date： 2016.10

Language：English  

Venue：Hamburg   Country：Germany  

Metal injection molding (MIM) process offers net shape production and high cost efficiency in order to produce the materials with poor workability such as Ti-6Al-4V. In our previous studies, injection molded Ti-6Al-4V showed high tensile strength and elongation comparable to those of wrought materials. However, fatigue strength of injection molded Ti-6Al-4V was lower than that of wrought materials because of large grain size and retained pores. In this study, the grain size of MIM Ti-6Al-4V compacts was decreased by addition of TiB2 powder and using the fine powder. As a result, the 0.4 mass% Boron added compacts treated HIP showed the fine grain size. Therefore, 93 % of fatigue strength compared to that of wrought material was obtained. In addition, the relationship of grain size and fatigue strength showed good agreement with Hall-Petch relations.

Event date： 2016.8

Language：Japanese  

Country：Japan  

Event date： 2015.5

Language：English  

Venue：San Diego   Country：United States  

Ti-6Al-4V alloy is paid the attention from the automotive and aerospace industries because of its outstanding specific strength and corrosion resistance. On the other hand, Ti-6Al-4V alloy has normally poor workability. Therefore, Metal Injection Molding (MIM) process is hoped to be one of the technique to reduce the manufacturing cost. Recently many researches for Ti-6Al-4V compacts by MIM process were reported, however, there are a few reports about fatigue fracture properties. According to our previous study, they presented a problem of low fatigue strength compared to wrought material. In this study, to improve the fatigue strength of Ti-6Al-4V compacts by MIM process, a little amount of boron was added by using TiB2 powder. Boron showed the effect of refining the grain size of lamellar structure of Ti-6Al-4V compacts, which lead to increase the fatigue strength.

Event date： 2010.10

Language：English  

Venue：Florence   Country：Italy  

Generally, the mechanical properties of conventional P/M materials are inferior to those of wrought materials. Therefore, the improvement of mechanical properties for P/M materials is needed for heavy-duty applications such as automotive transmission gears. Heat-treated 4600 steel MIM compacts with heterogeneous microstructure, which are made possible using mixed elemental powders, showed excellent tensile and bending fatigue strength in our previous studies. This study was performed to clarify the relationship between rolling contact fatigue behavior and the microstructure in 4600 steel P/M compacts using prealloyed and mixed elemental powders. The heterogeneous microstructure using mixed elemental powders showed slightly superior properties compared with the homogeneous microstructure using prealloyed powder. Those compacts were also densified by rolling. Contrary to the prediction, the rolling contact fatigue strength of the rolled sample was on the same level as the non-rolled sample.