Journal of Japan Institute of Light Metals
Online ISSN : 1880-8018
Print ISSN : 0451-5994
ISSN-L : 0451-5994
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Volume 53, Issue 11
Displaying 1-17 of 17 articles from this issue
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REVIEW
RESEARCH REPORT
  • Effect of pre-aging on aging behavior in the early stage of aging at high temperatures for Al–Mg–Si alloys
    Makoto SAGA, Yukio SASAKI, Masao KIKUCHI, Akira HIBINO, Mamoru MATSUO
    2003 Volume 53 Issue 11 Pages 516-522
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.516
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    Effect of pre-aging on the behavior in the early stage of aging at high temperature for Al–0.81mass% Si–0.64mass% Mg alloy has been studied by means of hardness measurement, electric resistivity measurement, differential scanning calorimetry and transmission electron microscopy.
    Pre-aging temperature influenced on the subsequent aging behavior at high temperature. G.P.I zones were formed during the pre-aging below about 343 K, which were stable and remained in the early stage of the subsequent aging at 448 K. Therefore, G.P.I zones coexist with β″ phase in the alloy aged at 448 K for 1.8 ks after pre-aged below about 343 K, and the microstructure is coarse and sparse. This leads to the decrease in hardness.
    On the other hand, β″ phases were directly formed during the pre-aging above 343 K. And the microstructure is fine and dense in the alloy aged at 448 K for 1.8 ks after pre-aged above 343 K, which leads to the higher hardness.
    In order to get higher paint bake hardenability for the Al–Mg–Si alloy, it is important to suppress the formation of G.P.I zones before the bake hardening treatment.
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  • Influence of iron content on mechanical properties of Al–Mg–Si alloy sheets
    Tadashi MINODA, Hidetoshi UCHIDA, Kazuhisa SHIBUE, Hideo YOSHIDA
    2003 Volume 53 Issue 11 Pages 523-527
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.523
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    The influence of iron content on mechanical properties of Al–1.0mass%Si–0.5mass%Mg–0.1mass%Mn alloy T4 sheets was investigated. The amount of Al–Fe–Si second phase particles increased with iron content, thus silicon atoms were consumed by formation of Al–Fe–Si particles. Furthermore, tensile strength of the samples in T4 condition was not influenced by iron content, but the paint bake response decreased over 0.5 mass%. This was the result of lowering age hardening rate at the early stage of artificial aging because of the loss of silicon atoms. Also, bendability of the samples became worse with iron content. But, it was the worst at 0.5 mass% of iron content, while it at over 0.5 mass% became better or the same. The reason was considered as below. Cracking by bending occurred along the second phase particles and the shear bands. And the amount of second phase particles increased with iron content, whereas the formation of shear bands decreased with iron content over 0.5 mass% because of the loss of silicon. In addition, formability became worse slightly with iron content.
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  • Effects of Cu, Ag and Au addition on total elongation and fracture morphology in Al–Mg–Si alloys
    Kenji MATSUDA, Kousuke KIDO, Tokimasa KAWABATA, Yasuhiro UETANI, Susum ...
    2003 Volume 53 Issue 11 Pages 528-533
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.528
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    The effect of the addition of copper, silver and gold on age-hardening, total elongation and fracture morphology of Al–Mg–Si alloys was investigated by hardness measurement, tensile test, observation of fracture surface by scanning electron microscopy, and transmission electron microscopy. The addition of copper for the base and excess Si alloys increased the peak hardness of alloys, while the addition of silver or gold did not show any modification of peak hardness. The total elongation of alloys bearing copper, silver or gold was improved, when the tensile test was performed for peak aged alloys. Fracture surfaces of alloys bearing copper, silve or gold included the region of transgranular fracture, while those of alloys without additional elements were mainly intergranular fracture. Surface relief and fine slip bands were observed on fractured samples of alloys bearing additional elements. Mean width of precipitate free zones (PFZ) in alloys bearing additional elements was narrower than that without additional elements. According to results of this work, it is considered that additional elements of Cu, Ag and Au improve total elongation of peak-aged Al–Mg–Si alloy because prior deformation around grain boundaries during tensile deformation was controlled by the formation of narrower PFZ than alloys without these elements.
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  • Effects of microstructure on bendability of Al–Mg–Si alloys
    Akira HIBINO, Toshiki MURAMATSU, Makoto SAGA, Ken TAKATA
    2003 Volume 53 Issue 11 Pages 534-541
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.534
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    To reduce the weight of vehicle body structures, Al–Mg–Si alloys which benefit from artificial aging during paint bake cycle have been used in outer panels of automobiles. One of important requirements in these alloys is their ability to resist fracture in hemming. In this paper, the effect of Si and Fe contents on the bendability of Al–Mg–Si alloys has been investigated. The bendability is declined with increasing Si and Fe contents in these alloys. It is obvious that bendability is related to size distribution of second phase particles. Small cracks on the surface of a specimen seem to appear in the interface between second phase particles and matrix during bending test and many particles can be observed near an initial crack line across several grains on the surface. Intragranular crack formation and propagation play an important role in the mechanism of bend crack occurrence.
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  • Microstructure and mechanical properties of friction-stir-welded 6061 aluminum alloy sheets
    Shinji KUMAI, Gosuke WAKANA, Masato YAMAWAKI, Kwang-Jin LEE, Akikazu S ...
    2003 Volume 53 Issue 11 Pages 542-547
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.542
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    The 6061-0 aluminum alloy sheet with two millimeter thick was welded by friction-stir-welding (FSW) at various welding conditions. Microstructure of the welds was investigated by optical microscopy in order to characterize the plastic flow pattern in the weld and change in size and morphology of the matrix grain structure from the original pancake-like structure in the parent sheet. The transverse cross section in the weld revealed that the boundary between the stir zone and the TMAZ (thermo-mechanically-affected-zone) exhibited a linear shape from the top to the bottom through the sheet thickness. An onion-ring pattern, which was common in the friction-stir-welded thick plate, was not detectable in the present stir zone. The wavy striations were observed in the transverse- and longitudinal-cross section of the weld. These were traces of the oxide films on the butt surface of the parent sheet and these provided the base for the evaluation of characteristic plastic flow in the friction-stir welded thin sheet. Yield strength and UTS of the weld were almost equivalent to those of the parent sheet. On the other hand, the reduced elongation was obtained. The weld was shown to break in the HAZ (heat-affected-zone).
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  • Microstructures and mechanical properties of laser welds of 6061 aluminum alloy sheets pre-coated with lubricating film
    Kwang-Jin LEE, Shinji KUMAI, Akikazu SATO
    2003 Volume 53 Issue 11 Pages 548-553
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.548
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    In order to reveal the laser weldability of Al–Mg–Si alloys pre-coated with lubricating film, microstructure and mechanical properties were investigated in pre-coated 6061-O and -T4 aluminum alloy joints. Two types of laser (CO2 and YAG) were used for welding. No significant reduction in ultimate tensile strength (UTS) was observed in the pre-coated 6061-O joints regardless of the type of laser. The YAG-laser welds of pre-coated 6061-T4 alloy showed 20% reduction in UTS compared to that of the parent alloy. This amount of reduction was similar to that of the non-coated alloy joints. On the other hand, for the CO2 laser welds, UTS drop of the pre-coated joints was 50%. This was larger than the 30% reduction of the non-coated alloy joints. The reduction of UTS in the CO2 laser weld was attributed to a large number of porosity in the weld metal.
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  • Mechanical and corrosion properties of 6061 aluminum alloys recycled by hot-extrusion of cutting chips
    Kazutaka SUZUKI, Ichinori SHIGEMATSU, Yuan-bin XU, Tsunemichi IMAI, Na ...
    2003 Volume 53 Issue 11 Pages 554-560
    Published: 2003
    Released on J-STAGE: March 30, 2007
    DOIhttps://doi.org/10.2464/jilm.53.554
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    From cutting chips of 6061 aluminum alloy, recycled materials' plates were fabricated by extrusion and rolling. Three kinds of cutting chips, which were dry-cutting chips without cutting oil, wet-cutting chips with cutting oil and clean chips obtained by washing of the wet-cutting chips, were used for the recycling process. Moreover, non-recycled materials' plates which processed by the same extrusion and rolling using virgin materials of the same alloy as the case of the recycled materials were prepared for comparison. These four kinds of plates were characterized by carrying out ultimate analysis by fluorescent X-ray spectrometer and infrared absorption spectrometer, optical microscopic and SEM observation, tensile test, and corrosion test. Consequently, a significant difference in structures, tensile properties, and corrosion resistance was not recognized among three kinds of recycled materials, it became clear that cutting oil and detergent hardly influence the characteristics. Moreover, it was found that recycled materials had smaller crystal grain than that of non-recycled materials, and excelled in both strength and corrosion resistance. The conclusion that recycling of the cutting chips by extrusion and rolling was very promising in 6061 aluminum alloys was obtained.
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