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Volume 58, Issue 12
Displaying 1-7 of 7 articles from this issue
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RESEARCH REPORT
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Yoshihiko Hangai, Soichiro KitaharaArticle type: Research Report
2008 Volume 58 Issue 12 Pages 639-643
Published: December 30, 2008
Released on J-STAGE: January 30, 2009
JOURNAL FREE ACCESSPore formation in high-pressure die casting is inevitable and pores adversely affect the mechanical properties and pressure tightness. Pores are induced by solidification shrinkage or entrapment of gas. To eliminate pores in die castings in the foundry floor, accurate identification of predominant cause of pores is essential. In this paper, the unbiased quantitative evaluation is proposed so that die casters can take corrective action to reduce pores. We proposed fractal dimension of shape and spatial distribution of porosity perimeter as the quantitative indicator of the identification of pores, namely, shrinkage or gas entrapment. The purpose of the present investigation is to demonstrate the validity of the proposed fractal dimensions by comparing the pores in different regions of die castings, which vary widely in porosity distribution. The proposed fractal dimensions are clearly different from inner region (shrinkage and gas induced pores are mixed) and surface region (only gas induced pores exist) in the die castings.View full abstractDownload PDF (1757K) -
Takahiko Nakamura, Shinji Iwama, Shin-ya KomatsuArticle type: Research Report
2008 Volume 58 Issue 12 Pages 644-649
Published: December 30, 2008
Released on J-STAGE: January 30, 2009
JOURNAL FREE ACCESSMg and Si contents in mass% written as {Mg} and {Si} was read out from solid solubility isotherms in Al rich corner of Al–Mg–Si phase diagram recommended by Willey. The Mg richer side than locus of apex for (Al) –Mg2Si– (Si) three phases region was named as region A and another side richer in Si than the locus as region B. Relation between complete dissolution temperature TCD and the Mg and Si contents in the region A can be written as
ln [ {Mg} 1.73 {Si} ] = (12.1±0.2) − (1.06±0.01) ×104/TCD .
In the region B, writing linear relation between {Mg} and {Si} as
{Mg} =α {Si} +β
and under assumption that the β shows an Arrhenius type temperature dependence, a relation
ln [ {Mg} +2.43 {Si} ] = (8.16±0.03) − (5.77±0.03) ×103/TCD
was obtained. Tracing change in resistivity with temperature of heat treatment, the TCD of commercial alloys was experimentally estimated. Experimental TCD values well coincided with calculated values in 6N01, 6151 and previously investigated 6063 alloys which are low contents in the region A. However, perhaps because of existence of coarse Mg2Si particles which require long period of high temperature heat treatment to dissolution, high contents 6061 in the region A and 6022 in the region B showed experimental values about 20 K lower than the calculated values.View full abstractDownload PDF (509K) -
Hidetoshi Takagi, Yasuhiro Uetani, Masayoshi Dohi, Toru Watanabe, Tomo ...Article type: Research Report
2008 Volume 58 Issue 12 Pages 650-655
Published: December 30, 2008
Released on J-STAGE: January 30, 2009
JOURNAL FREE ACCESSIn order to improve on the quality of Al–Si alloy billets, which are used as the feed stock for precision forging, a new vertical semi-continuous casting process has been adopted using a heat insulating and rapid cooling mold (HI-RCM) casting process. In our study, 4032 aluminum alloy billets with smooth surfaces have been obtained by controlling casting rates of HI-RCM process. Distributions of primary silicon, eutectic structure and secondary dendrite arm spacing (DAS) in the conventional DC casting billets were compared with the smooth surface billets fabricated by HI-RCM casting process under optimum conditions, and the latter one had finer and more homogeneous microstructures than those in the former billets.View full abstractDownload PDF (3180K) -
Naoki Mizuta, Kiyotaka Matsuura, Munekazu Ohno, Yoshinari Miyamoto, So ...Article type: Research Report
2008 Volume 58 Issue 12 Pages 656-661
Published: December 30, 2008
Released on J-STAGE: January 30, 2009
JOURNAL FREE ACCESSA new titanium aluminide coating method on titanium surface has been proposed, which is characterized by arc surface melting of an aluminum plated titanium surface. The arc surface melting was performed using a computer aided 3-dimensional micro welder (3DMW) designed by the present authors. The arc heat melted the aluminum plated titanium surface and produced a titanium aluminide layer of a ~300 μm thickness on the surface of titanium substrate. The titanium aluminide coated sample exhibited 500–700 in Vickers hardness number and excellent wear resistance.View full abstractDownload PDF (3949K) -
Yoshihiro Nakayama, Kazunobu YamadaArticle type: Research Report
2008 Volume 58 Issue 12 Pages 662-667
Published: December 30, 2008
Released on J-STAGE: January 30, 2009
JOURNAL FREE ACCESSIt is well known that plastic deformation results in formation of deformation bands for some aluminum alloy sheets. However, there are few reports dealing with the formation characteristics of deformation bands, such as a position and an order of deformation bands. 5083-O aluminum alloy sheet was tensile deformed in order to investigate in detail the formation characteristics of deformation bands. The tensile test was carried out at 318 K and the effects of cross head speed on the formation characteristics were also examined. Many of second deformation band were formed to the first one in the partially overlapping shape, and a similar tendency was ascertained about the deformation band afterwards. Since the deformation bands formed in the early stage had a tendency to generate in the order, the formation behavior of deformation bands was possible to classify into two patterns. The ordering formation of deformation bands was affected by both an interruption period of tensile test and a geometrical shape of previously formed deformation bands. It is thought that microstructure changes due to atomic diffusion brought the variation of ordering formation of deformation bands. The amplitude of a load fluctuation in the load versus displacement curves was changed depending on the position where the deformation band was formed.View full abstractDownload PDF (565K) -
Toshiki Maezono, Masatsugu SaitoArticle type: Research Report
2008 Volume 58 Issue 12 Pages 668-673
Published: December 30, 2008
Released on J-STAGE: January 30, 2009
JOURNAL FREE ACCESSIn recent years, as electronic equipments become more compact and have higher performance, the problem of heat is being aggravated. As a way to solve this problem, pre-coated aluminum sheet has been noticed. It is known that black additives-containing coating film has the relatively good thermal radiation. However, the detailed reports on the effects of resin types and black additives in coating films are few. Therefore, we studied in detail the effects of resin types and graphites in coating films on heat radiating properties of pre-coated aluminum sheet. In this paper, we consider that the chemical structure of the resin in coating films is closely related with the spectral emissivity. Especially emissivity of polyester cured by melamine is good. It is possible for graphite to improve the emissivity of the wide wavelength range 4.5~14.2 μm, It was found that the average particle size 7.0 μm of amorphous graphite is effective especially.View full abstractDownload PDF (1538K)
REVIEW
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Katsuyuki SuzukiArticle type: Review
2008 Volume 58 Issue 12 Pages 674-678
Published: December 30, 2008
Released on J-STAGE: March 31, 2009
JOURNAL FREE ACCESSDownload PDF (1647K)
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