Isesaki, Japan
Isesaki, Japan

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Hangai Y.,Gunma University | Takahashi K.,Gunma University | Kato H.,Gunma University | Utsunomiya T.,Shibaura Institute of Technology | And 3 more authors.
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2011

The nondestructive quantitative evaluation of pore morphology of porous aluminum, which uses fractal dimensions of spatial distribution of pore area DA, is proposed. The purpose of this paper is to investigate the validity of proposed evaluation by comparing pore morphology in two different types of porous aluminum which were fabricated from different starting materials. It was shown that DA can be expected to provide the sufficient information to quantitatively characterize the morphology of pores in porous aluminum. © 2011 The Japan Institute of Metals.


Utsunomiya T.,Shibaura Institute of Technology | Takahashi K.,Gunma University | Hangai Y.,Gunma University | Kitahara S.,Gundai Co.
Materials Transactions | Year: 2011

Porous aluminum is expected to be applied as a multifunctional material in various industrial fields because of its light weight and high energy absorption. When aluminum alloy die castings are used as a starting material in the fabrication of porous aluminum, it can be expected that, by effectively using the gases intrinsically contained in the die casting to generate pores, porous aluminum can be fabricated by adding a small amount of blowing agent. In this study, while systematically varying the amount of blowing agent from 0 to 1.4mass% that is added to ADCl2 aluminum alloy die castings containing three different amounts of gases, porous aluminum is fabricated by the FSP (friction stir processing) route precursor method. Titanium(II) hydride powder is used as the blowing agent. The variations of porosity and pore structure with the amount of added blowing agent are investigated for each amount of gases contained in the die castings. On the basis of the results, it is shown that, by using a blowing agent of approximately 0.6mass%, ADCl2 porous aluminum with high porosity can be fabricated regardless of the amount of gases contained in the die casting. © 2011 The Japan Institute of Metals.


Hangai Y.,Gunma University | Kato H.,Gunma University | Utsunomiyav T.,Shibaura Institute of Technology | Kitahara S.,Gundai Co. | And 2 more authors.
Materials Transactions | Year: 2012

Aluminum foam was fabricated without the use of a blowing agent by a friction stir processing route using ADC12 aluminum alloy die castings, which contain a large number of gas pores. In this study, ADC12 foams with a porosity of 5077% were successfully fabricated, and the pore structures and compression properties of the obtained ADC12 foams were investigated. The ADC12 foams had smaller pores than commercially available aluminum foam. Moreover, the pore size of the ADC12 foams was almost the same regardless of the porosity. According to the results of compression tests, the plateau stress and energy absorption tend to decrease with increasing porosity. Commercially available aluminum foam exhibited higher energy absorption at a low compression stress, whereas the ADC12 foams exhibited higher energy absorption at a high compression stress. Also, the ADC12 foams with higher porosity exhibited higher energy absorption per unit mass, regardless of the compression stress. In contrast, the energy absorption per unit volume was greatest for the low-porosity ADC12 foam at a low compression stress but greatest for the high-porosity foam at a high compression stress. © 2012 The Japan Institute of Metals.


Hangai Y.,Gunma University | Kato H.,Gunma University | Utsunomiya T.,Shibaura Institute of Technology | Kitahara S.,Gundai Co.
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2010

Porous aluminum was fabricated without the use of a blowing agent by friction stir processing using the gases contained in ADC12 aluminum alloy die-casting plates. The compressive properties of the obtained porous aluminum were investigated. It was shown that a compressive test specimen with a porosity of approximately 70% was obtained that had pores with a relatively small area and high sphericity. Porous aluminum fabricated without the use of a blowing agent exhibited brittle fracture at a relatively high plateau stress and high absorption energy compared with those of ALPORAS. © 2010 The Japan Institute of Metals.


Hangai Y.,Gunma University | Kato H.,Gunma University | Utsunomiya T.,Shibaura Institute of Technology | Kitahara S.,Gundai Co. | And 2 more authors.
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2010

Various types of ADC12 aluminum alloy die casting plates containing different amounts and types of gases were fabricated by varying the die casting conditions. Porous aluminum without the use of a blowing agent was fabricated by friction stir processing using the gases contained in the fabricated ADC12 aluminum alloy die casting plates. The effect of the amount of gases contained in the die castings on the foaming efficiency and the pore structures of obtained porous aluminum observed by X-ray CT inspection were investigated. It was shown that, although the expansion efficiency of each type of gas was not clear, the total amount of gases and porosity of obtained porous aluminum has good correlation. A porosity of approximately 60% was obtained with small area of pores and highly spherical. © 2010 the Japan Institute of Metals.


Hangai Y.,Gunma University | Kuwazuru O.,University of Fukui | Yano T.,Gunma University | Utsunomiya T.,Shibaura Institute of Technology | And 5 more authors.
Materials Transactions | Year: 2010

The geometric features of clustered shrinkage pores (CSP) in ill-conditioned aluminum alloy die castings were revealed and their effect on the fatigue strength was discussed. To obtain the geometric features of CSP, an observation using a commercial microfocus X-ray computed tomography (X-ray CT) system was carried out and the position and size of CSP were confirmed. However, the detailed geometry of the CSP could not be clearly observed by X-ray CT, because each pore in the CSP was too small to observe owing to the insufficient resolution of the CT image. We developed a serial sectioning system with a polishing machine and an optical microscope. Observation using the serial sectioning system clearly showed that a CSP consists of many interconnected small pores, which formed an extremely complicated shape. The CSP was thought to grow from relatively large gas pores, which connect to small pores and consequently generate a cavity with a huge volume and a complicated geometry. The complex geometry of CSP resulted in the concentration of stress around CSP, and significantly undermines mechanical properties such as tensile strength and fatigue strength. © 2010 The Japan Institute of Metals.


Hangai Y.,Gunma University | Kato H.,Gunma University | Utsunomiya T.,Shibaura Institute of Technology | Kitahara S.,Gundai Co.
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2010

Porous aluminum was fabricated by friction stir processing using the gases intrinsically contained in aluminum alloy die castings without the use of a blowing agent. The effect of the amount of gases contained in the die castings on the foaming efficiency was nvestigated. Although the expansion efficiency of each type of gas was not clear, the total amount of gases was sufficient to obtain high porosity. A porosity of approximately 60 pct was obtained with highly spherical and fine pores. © The Minerals, Metals & Materials Society and ASM International 2010.


Hangai Y.,Gunma University | Takahashi K.,Gunma University | Utsunomiya T.,Shibaura Institute of Technology | Kitahara S.,Gundai Co. | And 2 more authors.
Materials Science and Engineering A | Year: 2012

Functionally graded aluminum (FG) foam with varying pore structure was fabricated by utilizing friction stir processing. Die castings containing a large amount of gas were used as the starting material. The obtained FG foam had two different deformation stages and two plateau regions with a seamless bonding interface. © 2011 Elsevier B.V.


Hangai Y.,Gunma University | Takahashi K.,Gunma University | Yamaguchi R.,Gunma University | Utsunomiya T.,Shibaura Institute of Technology | And 3 more authors.
Materials Science and Engineering A | Year: 2012

Cellular materials are expected to be used for the components of automobiles and as railway and building materials owing to their lightweight structures and desirable mechanical properties. The newest class of cellular materials consists of functionally graded aluminum (FG Al) foams, in which the properties vary with the position. In this study, closed-cell FG Al foam with a varying pore structure was fabricated and its deformation behavior during the compression tests was nondestructively observed by X-ray computed tomography (X-ray CT). The fabricated FG Al foam had different pore structures (different densities) in the same Al foam. The FG Al foam initially started to deform only in the low-density region, which was followed by deformation in the high-density region. The deformation of the FG Al foam indicated its novel mechanical properties, such as multiple plateau stresses, corresponding to the pore structures of the regions where deformation occurred. Consequently, it was shown that the FG Al foam with a varying pore structure and a seamless bonding interface has the potential to be deformed at a controlled and desired location and with a desired plateau stress. © 2012 Elsevier B.V.


Hangai Y.,Gunma University | Ishii N.,Gunma University | Koyama S.,Gunma University | Utsunomiya T.,Shibaura Institute of Technology | Kitahara S.,Gundai Co.
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2012

Porous metal is the multifunctional material with both light weight and high energy absorption properties. In this study, a composite structural material, which consists of ADC12 porous aluminum and dense steel plates, was fabricated using friction stir welding (FSW). ADC12 porous aluminum was fabricated by ADC12 aluminum alloy die castings containing large amount of gases without using blowing agent. It is expected that both fabricating precursor of ADC12 porous aluminum and bonding the precursor to steel can be conducted simultaneously by FSW. Composite material having a porosity of approximately 60% can be obtained at a holding temperature of 948 K and a holding time of 8 min. Fe-Al based intermetallic compound (IMC) layer with the thickness of approximately 20 m was observed at the interface. It was shown that IMC layer was formed at the foaming (heating) process by diffusion-limited process. © 2012 The Japan Institute of Metals.

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