Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 55, Issue 2
Displaying 1-9 of 9 articles from this issue
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RESEARCH REPORT
  • Wear resistance of aluminum bearing alloys containing high concentration of tin under boundary lubrication
    Michihiro TAGAMI, Akira SUGAFUJI, Ken-ichi OHGUCHI, Yohei SASAKI, Akir ...
    2005 Volume 55 Issue 2 Pages 57-62
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.57
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    The effect of the amount of Sn and Si contents on the wear resistance in the aluminum bearing alloys containing high tin content was investigated. The friction coefficient and abrasive loss of the as-cast aluminum alloys were measured against commercial stainless steel (SUS304) in the boundary lubrication. It was found that Al-11.8%Sn-4.6%Si-1.1%Cu alloy and Al-15.9%Sn-4.5%Si-1%Cu alloy had low friction coefficient and better wear resistance with contact pressure in the range from 0.2 to 0.4MPa, whereas friction coefficient and abrasive loss increased with increasing contact pressure, beyond 0.45MPa. Grey white phase (containing Sn and Si content) was formed on the worn surface in the Al-11.8%Sn-4.6%Si-1.1%Cu alloy and the formation of this phase had resulted in better wear resistance of aluminum bearing alloys containing high tin content in the boundary lubrication.
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  • Effect of tool rotation speed on the microstructure of the friction stir weld of an Al-Cu-Mg-Si alloy
    Sunao TANAKA, Masaki KUMAGAI, Hideo YOSHIDA
    2005 Volume 55 Issue 2 Pages 63-67
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.63
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    The effect of tool rotation speed on the microstructure in the friction stir weld of Al-1.7mass%Cu-1.0mass%Mg-0.8mass%Si alloy T4511 extrusions has been investigated. The increase of heat input with a rotation speed enlarged the grain size in the stir zone. A postweld heat treatment at 195°C for 8h hardly increased the hardness in the stir zone welded at a rotation speed of 1000 rpm and raised the density of the coarse precipitates, Al5Cu6Mg2 phase. At a rotation speed of 1500 rpm, however, the postweld heat treatment produced fine precipitates after the precipitated phase had been already dissolved during the friction stir welding, and increased the hardness of the stir zone up to the same level as that of the base metal T6511.
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  • Change in microscopic surface profile during tensile plastic deformation of high purity aluminum polycrystals
    Xiaoqun WANG, Takeji ABE, Naoya TADA, Ichiro SHIMIZU
    2005 Volume 55 Issue 2 Pages 68-74
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.68
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    Roughening on free surface in polycrystalline metal during plastic deformation is closely related to the inhomogeneous deformation in the respective grain at the surface. Uniaxial tensile tests were carried out on annealed pure aluminum sheet specimens with various grain sizes. The roughening was measured by a 3-dimensional stylus instrument in order to study the roughness change on both sides of specimen surface at each strain. The irregularities of surface shape on one side are found to be reversed on the backside, when the averaged grain size is as large as the thickness of the specimen. There are some deviations in the strains of the grains and their standard deviation increases with the applied strain.
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  • Influences of spatial distribution of Si particles on crack propagation in model Al-Si cast alloys
    Seishi NISHIDO, Lihe QIAN, Hiroyuki TODA, Toshiro KOBAYASHI, Mitsuo NI ...
    2005 Volume 55 Issue 2 Pages 75-81
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.75
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    In-situ SEM observation has been used to characterize crack propagation behaviors and microscopic damage evolution at Si particles in three model hypoeutectic Al-Si cast alloys with different eutectic microstructures. It was clarified that the extents of damage and crack propagation path are significantly affected by the microstructures. A crack propagates in an eutectic region in a gravity cast alloy with dendritic α phase. Meanwhile, in the case of a rheo-cast alloy, a crack often propagates into α phases. Generally, the observed tendencies appear to be dominated by the fundamental crack-tip shielding/anti-shielding behaviors. However, the actual crack paths can not be fully assessed only from the experimental efforts. The crack propagation simulations are therefore performed for this purpose. Similar complicated crack propagation paths are well reproduced in the simulations, thereby providing mechanistic insights for the crack deflection behaviors.
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  • Heat-impact bonding-strength value of plated iron film on piston assessed by microscratch testing
    Hiroshi YAMAGATA
    2005 Volume 55 Issue 2 Pages 82-85
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.82
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    The bonding strength of the plated 15 μm-thick iron-film on a permanent-mold-cast AC8A piston was investigated. The strength was evaluated by heat impact testing and micro-scratch testing. The plated film which came off in heat impact testing came off below a load value of 25N in micro-scratch testing. It was assessed that the stress on the substrate generated by the micro-scratch test of 25N load was 239MPa while that by the heat-impact test was 249MPa. A geometrical investigation concluded that the stress condition on the plated film generated by heat-impact testing is identical with that by micro-scratch testing.
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  • Solidified structure of a 5052 aluminum alloy obtained by semisolid casting
    LongYun PIAO, Tetsuichi MOTEGI
    2005 Volume 55 Issue 2 Pages 86-90
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.86
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    In this study, we performed semisolid casting of the 5052 aluminum alloy using an inclined cooling plate to find the casting conditions for the finest grain size in the solidified structure. The casting conditions in this experiment were pouring temperatures onto the inclined cooling plate, length and angles of the cooling plate, and thickness of BN coating on the cooling plate. Although the solid-liquid coexistence zone of the 5052 alloy is narrower than that of the AC4CH alloy, the inclined cooling plate is useful, and we obtained an average grain size of 60 μm. The BN coating film must be as thin as possible because of the significant undercooling of the molten alloy. Greater undercooling causes more increased nucleation and more increased number of crystals to grow on the cooling plate. As a result, fine and granular crystals were obtained. The thermal boundary layer between the BN coating layer and the molten alloy, and the undercooling of the molten alloy were influenced by the flow speed of the molten alloy on the plate.
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  • Effect of film thickness on fatigue strength of a TiAl alloy coated with TiAlN film at elevated temperature
    Takeshi KASUYA, Hideto SUZUKI
    2005 Volume 55 Issue 2 Pages 91-96
    Published: 2005
    Released on J-STAGE: February 24, 2006
    DOIhttps://doi.org/10.2464/jilm.55.91
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    The fatigue strength of TiAl intermetallic alloy coated with TiAlN film was studied in vacuum at 1073 K using a SEM-servo testing machine. In addition, three kinds of TiAlN films were given by physical vapor deposition (1,3 and 10 μm). The fatigue strength of 3 μm was highest. Also, the fatigue strength of 1 μm was lowest. From this result, existence of optimum film thickness was suggested because the difference of fatigue strength arose in each film thickness. The justification for existence of optimum film thickness is competition of 45-degree crack and 90-degree crack. The 45-degree crack is phenomenon seen in the thin film (1 μm), and is caused by plastic deformation of TiAl substrate. The 45-degree crack is the factor of the fatigue strength fall by the side of thin film. In contrast, the 90-degree crack is phenomenon in the thick film (10 μm), and is caused as result of reaction against load to film. The 90-degree crack is the factor of the fatigue strength fall by the side of thick film. In conclusion, the optimum film thickness can perform meso fracture control, and improves fatigue strength.
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