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Volume 58, Issue 4
Displaying 1-5 of 5 articles from this issue
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RESEARCH REPORT
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Shuhei Osaki, Thoru Harano, Jun Ikeda, Kohji Ichitani, Pizhi ZHAO, Yos ...Article type: Research Report
2008 Volume 58 Issue 4 Pages 139-145
Published: April 30, 2008
Released on J-STAGE: May 30, 2008
JOURNAL FREE ACCESSFor 6061-T6 aluminum alloy plates with fine- or coarse-grained structure, SSRT (slow strain-rate technique) in humid air was carried out using a smooth or notched tensile specimen to evaluate the susceptibility to hydrogen embrittlement and to demonstrate the hydrogen effect on fracture process. The fine-grained materials under the hydrogen environment showed little change in tensile properties compared with the inert environment of dry nitrogen gas, while the coarse-grained materials exhibited some change in ductility; namely a decrease for the smooth specimen and an increase for the notched specimen. Although the materials ruptured by ductile fracture independently of grain size, the characteristic feature that coarse slips and void formation were promoted by hydrogen was observed. It is therefore suggested that the nature of hydrogen effect in 6061-T6 alloys is an enhancement of ductile fracture. As the increase in grain size leads to encourage the hydrogen effect, the grain coarsening should be restrained.View full abstractDownload PDF (4715K) -
Masafumi Kokubo, Yoshimasa Takayama, Shinichi Kazui, Takao Kaneuchi, H ...Article type: Research Report
2008 Volume 58 Issue 4 Pages 146-150
Published: April 30, 2008
Released on J-STAGE: May 30, 2008
JOURNAL FREE ACCESSADC12 and 5052 dissimilar aluminum alloys have been connected by friction stir welding (FSW). The temperatures at the stir zone and at four points on each outside of the joint line were measured during FSW in various conditions. After FSW, the tensile test was carried out in the direction perpendicular to the joint line. Tensile strength did not depend on the traveling speed, and indicated an almost constant value by about 88% of mother material strength. However, the necking feature in the breaking part was influenced by the traveling speed. That is, the necking was caused at low traveling speeds of FSW while it was hardly caused at high traveling speeds. The two-dimensional hardness distribution in the WD section was measured for various FSW conditions. The material flow with stirring and the spatial difference of the hardness distribution appeared at various traveling speeds. The stirred region consisting of stir zone and thermomechanical affected zone and the softened part in the stir zone were wider in the 5052 side at lower traveling speed. Softening in the 5052 side was scarcely observed in high traveling speeds. Moreover, the difference of softening in this 5052 was attributed to a difference in the heat input by changing the traveling speed.View full abstractDownload PDF (3240K) -
Pizhi Zhao, Takayuki Kobayashi, Takayuki TsuchidaArticle type: Research Report
2008 Volume 58 Issue 4 Pages 151-156
Published: April 30, 2008
Released on J-STAGE: May 30, 2008
JOURNAL FREE ACCESSThe correlation between compression conditions at temperatures in the range of 573–773 K with strain rate range of 0.002–2 s−1 and grain size after solution heat treatment (SHT) of 6061 aluminum alloy, was investigated. It is concluded that the grain coarsening occurred under specific Zener-Hollomon parameters of 108~2×1012 s−1. This phenomenon could be explained by crystalline orientation analysis and stored deformation energy evaluation. Small Z parameter condition could get low stored strain with fine grains which were stable during SHT. High Z parameter condition could get high stored strain, so a lot of small recrystallized grains were formed after SHT. Effect of Cr and Zr contents on the grain size of 6061 aluminum alloy was also investigated. Grains were fine when 0.34 mass%Cr or 0.17 mass%Cr and 0.14 mass%Zr were added due to pinning effects of Cr bearing dispersoids and Zr bearing dispersoids to grainboundaries.View full abstractDownload PDF (6750K) -
Nobuo Hattori, Masaki Tanigawa, Yoshiyuki Kawade, Masazumi OkidoArticle type: Research Report
2008 Volume 58 Issue 4 Pages 157-161
Published: April 30, 2008
Released on J-STAGE: May 30, 2008
JOURNAL FREE ACCESSPre-coated aluminum sheets are superior in cost performance and productivity compared to aluminum sheets coated after press forming. Functional pre-coated aluminum sheets, with superior surface characteristics such as lubricity and corrosion resistance have been increasingly used in electrical and other industrial fields. In this paper, the function of corrosion resistance was taken up among these surface functions. And the effects of the glass transition temperatures of the films on the corrosion resistance of pre-coated aluminum sheets before and after forming were investigated. The corrosion resistances after forming of polyester pre-coated aluminum sheets with three different glass transition temperatures were investigated by salt spray test. It was found that corrosion resistances of the film with glass transition temperatures higher than the forming temperature were low. In the samples with low corrosion resistance after forming, whitening of the film was observed. The corrosion reaction resistance values after forming of polyester pre-coated aluminum sheets with three different glass transition temperatures were also measured by electrochemical impedance spectroscopy test. It was found that corrosion reaction resistance values of the film with high glass transition temperatures showed the small values after stretching. It could recognize correlation in above two test results. After forming, micro cracks could be observed only in the sample with high glass transition temperature. This micro cracks made the corrosion resistance of the samples decrease.View full abstractDownload PDF (1925K)
REVIEW
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Hiroto HabuArticle type: Review
2008 Volume 58 Issue 4 Pages 162-166
Published: April 30, 2008
Released on J-STAGE: July 30, 2008
JOURNAL FREE ACCESSDownload PDF (2510K)
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