Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 58, Issue 3
Displaying 1-6 of 6 articles from this issue
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RESEARCH REPORT
  • Effect of grain boundaries on bending fatigue life of aluminum bicrystals with 0.5 schmid factor on primary slip systems
    Ken Atagi, Yoshihiro Okumoto, Kouji Nishimoto
    Article type: Research Report
    2008 Volume 58 Issue 3 Pages 93-97
    Published: March 30, 2008
    Released on J-STAGE: April 30, 2008
    DOIhttps://doi.org/10.2464/jilm.58.93
    JOURNAL FREE ACCESS
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    In order to examine the effect of grain boundaries on cyclic bending behavior, three types of aluminum bicrystals having a Schmid factor of 0.5 for the primary slip system of each component crystal and different disparities in plastic strain on the primary slip system between two component crystals were prepared by the Bridgman method. The component crystals A and B, the pseudo-bicrystals without grain boundary and the real grown bicrystals were investigated under the constant strain amplitude of 0.13% and cyclic frequency of 30.4 Hz at room temperature. The mixed model bicrystals without grain boundaries were prepared by joining two component crystals A and B. The cyclic saturation moments at 1000 cycles of the pseudo-bicrystals and the mixed model bicrystals were almost equal and were lower than that of real grown bicrystals with grain boundaries. It was suggested that the existence of grain boundaries contributed to the increase in the saturation moments and possibly shortened the fatigue lives.
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  • Effects of holding stress,temperature, and time in strain aging on flow curves of 5083-O aluminum alloy plate
    Yoshihiro Nakayama, Kakeru Yoshida, Kyohei Nomura
    Article type: Research Report
    2008 Volume 58 Issue 3 Pages 98-103
    Published: March 30, 2008
    Released on J-STAGE: April 30, 2008
    DOIhttps://doi.org/10.2464/jilm.58.98
    JOURNAL FREE ACCESS
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    It is well known that a strain aging was effective technique for a prevention of a strain marking in steel materials, whereas there are few reports on aluminum alloys on this issue. In the previous study, strain aged 5083 aluminum alloy plates were tensile deformed in order to investigate the effect of strain aging temperature and time on a generation of a stress fluctuation resulted in the strain marking. The findings suggested that a generation of stress fluctuation was affected not only by the strain aging temperature and time but also by the holding stress, which was applied to a specimen during the strain aging. In the present study, therefore, the strain aging in a wide range of holding stress was carried out, and the effect of holding stress on a generation of stress fluctuation was investigated. In addition, the influence of temperature, time, and holding stress during the strain aging on a generation of stress fluctuation was discussed in detail. Experimental results showed that the stress fluctuation tended to generate with increasing the holding stress. When the specimens were strain aged at the holding stress that corresponded to the flow stress when deformation was interrupted, the stress fluctuation that had been generated in a short aging time disappeared clearly as aging time extended.
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  • Mechanical properties of SiC particle–AZ31B magnesium alloy machined chips composites prepared by hot extrusion after ECAP
    Tetsuo Aida, Norio Takatsuji, Kenji Matsuki, Takuma Satou, Shigeharu K ...
    Article type: Research Report
    2008 Volume 58 Issue 3 Pages 104-110
    Published: March 30, 2008
    Released on J-STAGE: April 30, 2008
    DOIhttps://doi.org/10.2464/jilm.58.104
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    Wear resistance and mechanical properties of hot extruded AZ31B/SiC particle composite, where the hot extrusion billets were processed by ECAP, were investigated. Uniform dispersion of SiC particles was observed after extrusion for the mean particle size of 1.2∼11 μm constituting 0 to 6% volume fraction of SiC particle content, where the particles had been thinly adhered to the surface of the machined chips of ECAP-hot extrusion samples before extrusion. However, when the SiC particle size is under 3 μm, the aggregates at the triple junction of the interfaces of the machined chips could not be decomposed and dispersed. To solve this problem, hot extrusion was carried out using various cold green compacts prepared by repetitive ECAP processed up to 7 times. As a result, refinement of grain size was obtained for the ECAP extruded materials by decomposition and dispersion of the SiC particles with increase in the ECAP frequency. Consequently, it was possible to obtain the composite of AZ31 magnesium base alloy machined chip and SiC particle which contains almost uniformly dispersed SiC particles. Furthermore, the average grain diameter of the matrix was very much refined to approximately 2 μm, and σB, σ0.2 were also improved. Frictional wear test shows that abrasion resistance was further improved for N=7 extruded materials than N=4 samples due to more homogeneous mixing of the SiC particles as well as decomposition and dispersion of the aggregates.
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  • Improvement of surface roughness of aluminum products by the micro-grooves on tool surface in cold extrusion
    Shunpei Kamitani, Kenji Nakanishi, Samion Syahrullail
    Article type: Research Report
    2008 Volume 58 Issue 3 Pages 111-116
    Published: March 30, 2008
    Released on J-STAGE: April 30, 2008
    DOIhttps://doi.org/10.2464/jilm.58.111
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    The effects of the micro-groove arrays formed on the tool surface on the material flow, surface condition of a billet and surface quality of a product were investigated by carrying out the plane strain extrusion experiments. Paraffinic mineral oil and RBD palm olein were applied in the above experiments. The distributions of flow velocity and effective strain in a billet were analyzed by using the visio-plasticity method. The experimental and analytical results show that the extrusion load increases with the inflow of billet to the grooves. The results also show that the surface condition of the extruded product is smoother when the location of the micro-groove array is at the inner section in the deformation boundary and a paraffinic mineral oil was used. The surface quality of a product in an extrusion process could be improved, under a slight rise of the extrusion load by using a tool with micro-groove arrays were formed on the tool surface at an appropriate section.
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