MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 52 , Issue 5
Showing 1-41 articles out of 41 articles from the selected issue
  • Jürgen Hirsch
    2011 Volume 52 Issue 5 Pages 818-824
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    The main Aluminium applications as state-of-the-art in European cars are presented. The main established Aluminium alloys and their application in automotive parts are presented together with recent developments. Also new studies and innovative multi-material concepts are discussed where Aluminium light-weight solutions are compared with that of other materials, like new steels, magnesium, plastics and composites. In the “SLC” (Super-Light-Car) project these new concepts were tested in a multi-material body-in-white prototype for a VW Golf V car, reaching a 34% weight reduction within a cost increment of 7,8 €/kg saved, with suitable technologies for high volume assembly cycles. In the final SLC concept Aluminium is the material of choice, proving its leading role in innovative light-weighting of cars. Aluminium achieves weight savings of parts up to 50% while maintaining safety and performance in a cost efficient way, competing efficiently with other light-weight materials.
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  • K. Kashihara, W. Ikushima, Y. Miyajima, D. Terada, N. Tsuji
    2011 Volume 52 Issue 5 Pages 825-829
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    A {100} ⟨001⟩ pure aluminum single crystal specimen was deformed by accumulative roll bonding (ARB) up to 9 cycles (εeq=7.18) with lubrication. The 5- and 9-cycle processes developed weakened textures composed of {123} ⟨634⟩ and {112} ⟨111⟩. The {100} ⟨001⟩ areas existed even after the 9th cycle. The area fraction of {100} ⟨001⟩ was almost the same as that of the 2-cycle processed specimen. The average area fraction of {100} ⟨001⟩ was 4.8%. The cross slips by primary slip pairs may play an important role in maintaining the {100} ⟨001⟩ area. In the 5-cycle processed specimen, {123} ⟨634⟩ bands were observed in not only the center layer but also the one-eighth thickness layers close to the specimen surfaces. After the 7th and 9th cycles, {112} ⟨111⟩ was observed to form by further crystal rotation from {123} ⟨634⟩.
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  • Takuya Tamura, Toshiro Matsuki, Kenji Miwa
    2011 Volume 52 Issue 5 Pages 830-833
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    It is known that mechanical vibrations which applied during solidification affect microstructure refinement. However, it is not completely understood which factor of vibrations is important for microstructure refinement. Factors of vibrations are frequency, acceleration, velocity and amplitude. In this study, the effect of mechanical vibrations on microstructure refinement of Al-7 mass% Si alloys was investigated systematically. The mechanical vibrations were applied to the melt in an alumina crucible from about 923 K to 863 K, and the crucible was quenched in water at 863 K. As a result, it was found that the velocity of mechanical vibrations corresponding to the vibration energy is important factor for primary crystals refinement. The mechanical vibrations with high velocity regardless of frequency can refine the primary crystals. It is considered that the mechanical vibrations promote heterogeneous nucleation just below the liquidus temperature.
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  • Chakkrist Phongphisutthinan, Hiroyasu Tezuka, Tatsuo Sato
    2011 Volume 52 Issue 5 Pages 834-841
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 20, 2011
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    The effects of Fe, Mn and Fe/Mn-combined additions on the refinement of the spheroidized semi-solid α-Al grains in the wrought aluminum 6000 based alloy was investigated. The semi-solid microstructure control of Al-1.2%Mg-1.3%Si based alloys with Fe (1.0 mass%), Mn (0.7 mass%) and Fe/Mn-combined (1.0/0.7 mass%) additions was studied by the Deformation Semi-Solid Forming (D-SSF) process. This process consists of high deformation before semi-solid heating in order to introduce high density of dislocations and fragmentation of intermetallic compounds. Various second phase particles strongly affect the resultant α-Al grain size. The deformation process of the Fe-added alloy with a low rolling ratio produces fine α-Al grains with an average size of 76 μm, which is apparently smaller than that of the Fe-free alloy with an average α-Al grain size over 100 μm. The Mn addition required a high deformation ratio to achieve an average α-Al grain of 85 μm. The combination of Fe and Mn additions produces the finest grain size of 64 μm. The morphology of the Fe-intermetallic compound in the semi-solid forming process can be controlled by the cooling rate and Mn addition. The D-SSF process is a promising process to modify the harmful Fe impurity into the useful intermetallic compounds.
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  • Mark Easton, Cameron Davidson, David StJohn
    2011 Volume 52 Issue 5 Pages 842-847
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    Two of the most important microstructural features of alloys are the grain size and the secondary dendrite arm spacing (SDAS) and these two factors are shown to combine together to describe the grain morphology. Both grain refinement and the SDAS depend upon alloy composition through constitutional undercooling, but in different ways. It is shown that there is a ‘characteristic’ SDAS for each alloy at a particular cooling rate, and reducing the grain size causes the grain morphology to change from dendritic to cellular/rosette-like to globular or spherical. Increasing the cooling rate refines both the SDAS and the grain size, but reduces the SDAS more rapidly leading to finer, more dendritic grain structures. Particular ratios of grain size to SDAS are used to define each morphology and it is shown how these can assist with obtaining a required grain size and morphology through the use of solidification conditions and alloy chemistry.
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  • Yohei Harada, Shinichi Tamura, Shinji Kumai
    2011 Volume 52 Issue 5 Pages 848-855
    Published: May 01, 2011
    Released: May 01, 2011
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    A356 alloy was cast into permanent molds and subjected to T6 heat treatment. Two solutionizing (solution heat treatment) temperatures (540°C and 560°C) were used, with the holding time for each varied between 0 min and 240 min. Tear test specimens of 4 mm in thickness were machined from the castings. Tear toughness (UEp: unit crack propagation energy) was obtained from load-displacement curves. With increasing solutionizing holding time, eutectic silicon particles were found to become larger and mean interparticle distance was found to increase. The UEp of specimens solutionized at the higher temperature (560°C) increased with holding time until 120 min but decreased with longer holding times. SEM observation of fracture surfaces after tear testing revealed dimples originating from dispersed silicon particles within the eutectic phase. Fine dimples were also observed in the eutectic aluminum region in specimens with reduced UEp. These fine dimples were different from the dimples found to originate from the eutectic silicon particles.
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  • Min-Seok Kim, Shinji Kumai
    2011 Volume 52 Issue 5 Pages 856-861
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    Al-Si alloy strips with various Si compositions were cast by using high-speed twin-roll caster. The strip thickness measurement and microstructure observation were carried out. The strip thickness changed prominently with varying Si composition. The strip thickness change was considered to result from change in solidification manner (skin or mushy-type solidification) depending on freezing temperature range of the alloy. The solidified structure of the mid-thickness region is also greatly influenced by the freezing temperature range. Internal crack appeared at the mid-thickness region of 2 mass% Si strip, in which the central band consists mostly of globular grains and equiaxed dendrites. The internal cracking is considered to be related with residual liquid in the central band region and its solidification.
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  • Sung-Yong Shim, Dae-Hwan Kim, Young-Rok Seong, Su-Gun Lim
    2011 Volume 52 Issue 5 Pages 862-867
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    The cooling plate method is a simple and effective process for casting ingots in thixoforming feedstock. Analysis of variance (ANOVA) and the Taguchi design method were used in order to reveal the effect on microstructure of major factors in this paper. ANOVA was used to define the effect of parameters such as the pouring temperature, cooling plate angle, holding time after pouring and mold temperature. Among all the factors, pouring temperature exerted the greatest statistically significant effect, especially on grain size. To optimize the conditions to ensure reproducibility, the plate angle and holding time were varied to reduce the effect of the pouring temperature. In the results, a lower plate angle and an extended holding time with a pouring temperature just below the liquid point afforded the formation of a microstructure with rosette-shaped grains in semisolid metal (SSM) slurries. Furthermore, when this slurry was reheated to the liquid/solid temperature, the morphology of the grains was transformed into globular.
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  • Shohei Tamura, Satoshi Sumikawa, Takeshi Uemori, Hiroshi Hamasaki, Fus ...
    2011 Volume 52 Issue 5 Pages 868-875
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: March 30, 2011
    JOURNALS FREE ACCESS
    Elasto-plasticity behavior of type A5052-O and AA6016-T4 aluminum alloy sheets was examined by performing several experiments of uniaxial tension, biaxial stretching and in-plane cyclic tension-compression. Both sheets exhibit apparent r-value planar anisotropy, especially for AA6016-T4 it is extremely strong, while their flow stress directionality under uniaxial tension is not so significant. Both the sheets show strong cyclic hardening with weak Bauschinger effect. Such material behavior is well described by Yoshida-Uemori kinematic hardening model combined with an appropriate choice of anisotropic yield function.
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  • Atsushi Yamamoto, Masaaki Tsukamoto, Daisuke Okai
    2011 Volume 52 Issue 5 Pages 876-881
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    Recrystallization phenomena in an Al-Mg-Si alloy cold-rolled at 30 and 50% reduction rates were observed on the same area in specimens during annealing at 673 K using SEM-EBSD method. After recovery in a narrow sense occurred, coarse subgrain microstructures were formed by migrating high angle boundaries at both reduction rates. The coarse subgrain microstructure contained low angle boundaries, and orientation gradients were observed in contrast to the recrystallized microstructure. Lattice rotation due to cold-rolling was recovered in the coarse subgrain microstructures for the case of 30% reduction. When the specimen was cold-rolled at 50%, lattice rotation occurred over a broad range of angles. As a result, prior grain boundaries became unclear, and the majority of the subgrains were surrounded by high angle boundaries. Some of the subgrains showed the coarse subgrain microstructure, and the others grew into recrystallized grains.
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  • Ilya Nikulin, Alla Kipelova, Sergey Malopheyev, Rustam Kaibyshev
    2011 Volume 52 Issue 5 Pages 882-889
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    It was shown that extensive grain refinement takes place in an as-cast Al-5.4%Mg-0.5%Mn-0.1%Zr alloy subjected to severe plastic deformation under multi-directional forging up to a total true strain of ∼9 at 250 and 300°C. At a strain of ∼3, the deformed microstructure is mainly characterized by the formation of new grains along original boundaries and the development of well-defined subgrains within interiors of original grains. Upon further straining the misorientation of deformation-induced boundaries increases; new grains appear homogeneously both within grain interiors and along original boundaries. Decreasing temperature accelerates the transformation of low-angle boundaries (LABs) into high-angle boundaries (HABs). The resulted grain size evolved in this alloy was slightly less than that produced in an Al-6%Mg-0.35%Sc by severe plastic deformation under similar conditions. In addition, in the alloy belonging to Al-Mg-Mn-Zr system the formation of a fully recrystallized structure was found at a lower cumulative strain in comparison with the alloy belonging to Al-Mg-Sc system. This unusual difference associated with the fact that the Al-5.4%Mg-0.5%Mn-0.1%Zr alloy was initially subjected to solution treatment at a relatively low temperature of ∼360°C. Effect of homogenization annealing on phase composition of this alloy is discussed.
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  • Yukito Nakanishi, Toshiyuki Fujii, Susumu Onaka, Masaharu Kato
    2011 Volume 52 Issue 5 Pages 890-894
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: March 30, 2011
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    Ultrafine-grained (UFG) Al of 99.98∼99.99% purity was fabricated by equal channel angular pressing. Fully reversed tension-compression low-cycle fatigue tests were carried out under plastic strain control at various temperatures between 83 K and 300 K. At 300 K, UFG Al showed rapid cyclic softening. As test temperature decreased, cyclic softening became less significant and at 83 K, UFG Al showed cyclic hardening till saturation. Formation of shear bands and development of dislocation structure were the characteristic features of fatigued specimens. As test temperature decreased, the area fraction of shear bands on specimen surface decreased and at 83 K, shear bands could not be observed. In addition, local grain coarsening occurred except at 83 K. Formation of dislocation cell and wall structures became more frequent at lower temperatures and well-developed dislocation walls were formed in grains as small as 1.5 μm in size at 83 K.
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  • Iya I. Tashlykova-Bushkevich, Goroh Itoh, Vasiliy G. Shepelevich, Taka ...
    2011 Volume 52 Issue 5 Pages 895-899
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    The thermal desorption spectroscopy has been applied to analyse hydrogen desorption from foils of Al-Cr alloys containing up to 3.0 mol% Cr produced by centrifugal melt quenching. Surface morphology of the alloys was monitored using atomic force microscopy and scanning electron microscopy. It was revealed that hydrogen behaviour is strongly affected by microstructural features available due to rapid solidification and represents at least four hydrogen trap sites in Al-Cr alloys. The Cr atoms in lattice sites are identified as predominant trap site. The occupancy of dislocations was estimated to be rather high in contrast to vacancies and pores in alloys. The amount of hydrogen trapped by vacancies is drastically decreased with increase in Cr concentration. These hydrogen/microstructure interactions were discussed regarding rapidly solidified pure aluminum as well as traditionally processed aluminum samples.
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  • Tomo Ogura, Shoichi Hirosawa, Akio Hirose, Tatsuo Sato
    2011 Volume 52 Issue 5 Pages 900-905
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 20, 2011
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    The additions of microalloying tin and (silver and tin)-combination were performed to modify the precipitate microstructure in the vicinity of grain boundaries with precipitate free zones (PFZs) and mechanical properties in Al-Zn-Mg alloys. In the Sn-containing alloy, TEM observation showed that some precipitates were sparsely formed within the region of PFZs of the Al-Zn-Mg ternary alloy. The quantitative analysis of the chemical compositions in precipitates showed that tin mainly contributes to nucleation in the vicinity of grain boundaries through the suppression of the vacancy depletion. This is well explained by the favorable interaction of tin with vacancies. The (Ag+Sn)-containing alloy formed a very narrow PFZ width and corresponding tensile properties were remarkably improved, which shows that tin enables to reduce the amount of microalloyed silver in Al-Zn-Mg alloys.
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  • JaeHwang Kim, Equo Kobayashi, Tatsuo Sato
    2011 Volume 52 Issue 5 Pages 906-913
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    Two types of nanoclusters, i.e. Cluster (1) and Cluster (2), play a strongly important role in the bake-hardening (BH) response in Al-Mg-Si alloys. Different formation behaviors of two types of nanoclusters were studied by means of hardness, differential scanning calorimetry (DSC), electrical resistivity measurement, transmission electron microscopy (TEM) and high resolution TEM observation in the both Cu-free and Cu-added Al-Mg-Si alloys. As the results, Cluster (1) formed during natural aging at room temperature causes a deleterious effect, whereas Cluster (2) formed by the pre-aging at 100°C is effective for the suppression of the negative effect on the two-step aging behavior of the both Cu-free and Cu-added alloys. On the other hand, the microalloying of Cu strongly affects the nanocluster formation due to the strong interaction with Mg, Si atoms and vacancies. The first-principle calculation for the two-body interaction energies provides quite useful information to understand the early stage of the phase decomposition. The effects of nanoclusters and the Cu addition on the age-hardening behaviors of Al-Mg-Si alloys are discussed based on the multi-step age-hardening phenomena.
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  • Katharina Strobel, Mark A. Easton, Lisa Sweet, Malcolm J. Couper, Jian ...
    2011 Volume 52 Issue 5 Pages 914-919
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    In high strength 6000 series alloys dispersoids that form during heating to the homogenization temperature are used to improve fracture toughness and suppress grain growth during the extrusion process. However, these dispersoids can act as heterogeneous nucleation sites for non-hardening Mg-Si precipitates if quenching after extrusion is delayed. This leads to a reduced level of Mg and Si in solid solution and hence lower achievable strength and hardness. This phenomenon is called quench sensitivity. In this study, the hardening response of several 6000 series aluminium alloys is related to microstructural features, especially dispersoid density. Therefore, the alloys were quenched at varying rates after extrusion and age hardened to peak strength. Quench sensitivity is related to dispersoid density as well as to the enthalpy related to the precipitation of Mg-Si phase measured by DSC. The results suggest that in alloys containing dispersoids, quench sensitivity is primarily determined by the number density of dispersoids. However, effects associated with elements in solid solution cannot be ruled out. TEM investigations suggest that not only the general reduction of Mg and Si is responsible for the reduced mechanical properties, but that an inhomogeneous distribution of hardening precipitates might be another determining factor.
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  • Daisuke Shimosaka, Shinji Kumai, Federico Casarotto, Shuichiro Watanab ...
    2011 Volume 52 Issue 5 Pages 920-927
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    Al-5.5%Mg-2.3%Si-0.6%Mn alloy and Al-13%Mg2Si pseudo-binary alloy were cooled at various cooling rates during solidification. Morphological change of secondary particle was examined. Solidified structure of Al-5.5%Mg-2.3%Si-0.6%Mn alloy consisted of primary α-Al dendrites, Al-Mg2Si eutectic structure and Al6Mn particles. The most significant morphological change was from lamella Al-Mg2Si eutectic structure in the permanent mold cast and the die-cast product to refined and globular Mg2Si phase in the high-speed twin-roll cast product. In contrast, no morphological change was observed for Al6Mn particles. In order to investigate the effect of morphological change of Mg2Si phase on tear toughness, tear toughness tests were performed for Al-13%Mg2Si pseudo-binary alloy cast products produced by permanent mold casting and high-speed twin-roll casting. Unit crack propagation energy (UEp) of the high-speed twin-roll cast products was 5 times higher than that of permanent mold cast products. For permanent mold cast specimens, crack propagation occurred along the interface of plate-like Mg2Si/matrix of the eutectic solidified region and in Al-matrix. But fracture surface of high-speed twin-roll cast specimens was covered with fine dimples. Such difference of fracture mode is due to morphological change of Mg2Si phase from plate-like to globular by rapid cooling.
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  • Zhan Zhang, Ken Fortin, Andre Charette, Xiao-Guang Chen
    2011 Volume 52 Issue 5 Pages 928-933
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    The influence of 0.5% magnesium addition on the fluidity evolution and microstructure of aluminum and Al-12%B4C composites was investigated. It was observed that the magnesium addition reduced the fluidity of aluminum and the Al-B4C composites. Moreover, magnesium promoted the interfacial reactions between liquid aluminum and B4C in the Al-B4C composites. An adequate Ti addition in the composites could effectively limit the impact of magnesium on the interfacial reactions and significantly improve the fluidity by forming a dense TiB2 protective layer on the B4C particle surface. It was also found that a part of magnesium is consumed in the reaction product, which resulted in the reduction of magnesium available in the matrix. The effects of magnesium and titanium on the fluidity, interfacial reactions and magnesium redistribution were discussed.
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  • Makoto Kobashi, Masato Noguchi, Naoyuki Kanetake
    2011 Volume 52 Issue 5 Pages 934-938
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    One of the practical applications of porous aluminum is the core material for panel/foam sandwich structures. To manufacture the foam/panel sandwich structure by a powder processing route, a sheet type precursor is essential. Therefore, a foaming behavior of aluminum sheet precursor (pure Al, 6061Al and Al-7Si) was examined. The foaming behavior was examined by the projected area of a precursor recorded by two video cameras from horizontal (lateral-side observation) and vertical (top-surface observation) directions. Average diameters and vertical/horizontal Feret diameter ratios were used to evaluate pore morphology. Free foaming behavior of the sheet type precursors was extremely unidirectional along the compression direction of the rolled precursor. With regard to pure aluminum and 6061Al precursors, the pore morphology at the early stage of foaming was extremely anisotropic (flat shape), while the pore morphology became spherical when the specimen reached to the maximum expansion. As for the Al-7Si precursors, such flat anisotropic pores were not observed even at the early stage of foaming.
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  • Moonhee Lee, Yongbum Choi, Kenjiro Sugio, Kazuhiro Matsugi, Gen Sasaki
    2011 Volume 52 Issue 5 Pages 939-942
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
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    The unidirectional carbon fiber (CF) preform for carbon fiber reinforced aluminium (CF/Al) composites has been investigated in terms of the fabrication condition and the strength property. The CF preform which consists of CFs and Cu particles was fabricated by spark plasma sintering (SPS) process with different fabrication temperatures. In order to determine the infiltration pressure of molten Al to the CF preform, the compression test was performed to the CF preform. The unidirectional CF preform by SPS process was well formed with the fabrication temperature condition at 1123 K in accordance with the formation of Cu particle bridging between fibers and Cu deposition on fibers. The compression strength of the CF preform increased with increasing fabrication temperature. Besides, the CF preform was deformed such as fiber micro-buckling or fiber kinking phenomena over the maximum compression strength. The infiltration pressure of the molten Al can be decided under the maximum compression strength.
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  • Taku Iwaoka, Mitsuru Nakamura
    2011 Volume 52 Issue 5 Pages 943-947
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 20, 2011
    JOURNALS FREE ACCESS
    An oxide film is easily formed on the surface of magnesium and aluminum powders due to the high chemical reactivity of these metals. The sinterability of these powders is extremely poor for conventional powder metallurgy. At present, the behavior of the warm compaction method, which has been done using iron powder, is practically very interesting, because high density and strongly sintered materials are efficiently obtained. However, there are only a few reports on the sinterability of magnesium and aluminum powder mixtures by this method. In this study, to consider the sinterability of such mixtures, we examined the effect of the compaction temperature. The compacts that consist of these mixtures were consolidated by the warm compaction method, which was conducted in the temperature range from 301 to 423 K. The compacts were sintered in an argon atmosphere. As a result, the transverse rupture strength for the warm compaction was from 20 to 30 MPa higher than for the cold compaction. The increasing compaction temperature causes sufficient contact between the powder particles, and at the same time, plastic deformation of the powder particles readily occurs. This behavior induced by the warm compaction method would lead to a break down of the oxide films. As a result, sufficient bonding between the powder particles occurred, and the transverse rupture strength increased.
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  • Masayuki Aonuma, Kazuhiro Nakata
    2011 Volume 52 Issue 5 Pages 948-952
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    The friction stir welding (FSW) process is a solid-state joining process and the joining temperature is lower than that used in the fusion welding processes. Therefore, for dissimilar metal welding, FSW is considered to offer several advantages over fusion welding. The present work investigated the weldability of duralumin and titanium alloys using friction stir welding. The aluminum plates used in this work were 2024-T3 and 7075-T651, and the titanium plates used were pure titanium and Ti-6Al-4V. The average tensile strength of the Ti/2024 FSW joints was 311 MPa, and the tensile strength of the Ti/2024 joint was higher than that of the Ti/7075 FSW joint when the joining conditions were the same. A mixed region of Ti alloy and Al alloy was observed at the joint interface, and the joints mainly fractured at this region, where there was an intermetallic compound layer. In this region, a TiAl3 intermetallic compound was detected by XRD. Therefore, it can be understood that this TiAl3 intermetallic compound affects the tensile strength of butt joints.
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  • Mitsuhiro Watanabe, Keyan Feng, Yoshio Nakamura, Shinji Kumai
    2011 Volume 52 Issue 5 Pages 953-959
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
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    Lap joining of a pure aluminum plate and a low carbon steel plate was performed using friction stir spot welding. The aluminum plate was placed over the steel plate, a rotating welding tool was inserted into the aluminum plate, and the tip of the tool was dwelled above the aluminum/steel interface. Dwell time was controlled in the range of 0 to 120 seconds. The microstructure of the welding interface was examined by optical microscopy and scanning electron microscopy. Chemical composition analysis was carried out by energy dispersive X-ray spectroscopy. Welding was achieved for all dwell times. Refined grains were formed by plastic flow in the aluminum matrix close to the welding interface. Intermetallic compound layer was produced along the welding interface. Precise backscattered electron image observation and energy dispersive X-ray spectroscopy analysis revealed that the intermetallic compound layer consisted of an Al13Fe4 phase layer and an Al5Fe2 phase layer. The thickness of the layers increased in proportion to the square root of the dwell time. The parabolic coefficient K was 1.30×10−14 and 6.06×10−13 m2/s for the Al13Fe4 layer and the Al5Fe2 layer, respectively.
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  • Taichi Nishida, Tomo Ogura, Mitsuo Fujimoto, Akio Hirose
    2011 Volume 52 Issue 5 Pages 960-966
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 20, 2011
    JOURNALS FREE ACCESS
    Friction stud welding with zinc insert was applied to 5000 series aluminum alloys. A cone-shaped A5056 stud bolt was successfully friction-welded onto A5083 plate at low torque using zinc insert compared to that without zinc insert. This is considered to be contributed by a eutectic reaction between aluminum and zinc, which can effectively remove the oxide film and promote the joining. With bigger torque and longer welding time, the amount of residual zinc was reduced and high strength was achieved. On the other hand, a twist break between the stirred zone and the stud bolt increased during friction and this causes the decrease of tensile strength of the joint after a certain amount of torque. The results of micro-tensile test showed that strength at the edge of joint interface was higher than that at the center area regardless of zinc insert. From the experimental results, the joining process of the present friction stud welding classified into five processes, i.e. wear of stud bolt, start of joining, increase of tensile strength, decrease of tensile strength, and fracture during friction.
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  • Keisuke Ueda, Tomo Ogura, Shumpei Nishiuchi, Kenji Miyamoto, Toshikazu ...
    2011 Volume 52 Issue 5 Pages 967-973
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 20, 2011
    JOURNALS FREE ACCESS
    The effects of Zn-based alloys coating (Zn, Al-Zn and Al-Mg-Zn) on the bondability of steel/aluminum alloy dissimilar metals joints were evaluated, in order to achieve strength in lower welding current. In the joint with Zn-based alloys insert, the oxide film on the aluminum alloy was sufficiently removed through eutectic reaction of Zn-based alloys and aluminum. In the joint with Zn-coated steel (GI), higher welding current is necessary to discharge the zinc coating and the oxide film from the bonding interface sufficiently. The thinner aluminum plate after welding and the thick reaction layer cause the decrease of cross tensile strength in the joints with no coating steel (SPCC) and Al-Zn-coated steel. Using Al-Mg-Zn-coated steel, higher strength was achieved in a lower welding current. This is because Al-Mg-Zn-coating melted at lower temperature than Zn and Al-Zn-coating, and the removal of the coating material and the oxide film on the aluminum alloy were sufficiently performed in the lower welding current.
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  • Ki-Sang Bang, Kwang-Jin Lee, Han-Sur Bang, Hee-Sun Bang
    2011 Volume 52 Issue 5 Pages 974-978
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 20, 2011
    JOURNALS FREE ACCESS
    Friction stir welding (FSW) was performed about AA6061-T6 and Ti-6Al-4V alloy sheets. A unique shaped tool with circular truncated cone of probe was used. Mechanical properties and interfacial microstructure were evaluated using tensile test, hardness test, optical microscopy (OM), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), respectively. Root area of probe in stir zone (SZ) reveals a mixture of finely recrystallized grains of Al and Ti particles pushed away from the base metal by strong stirring of probe. The joint interface of tip area of probe was relatively flat because stirring between aluminum and titanium alloy was not occurred due to the gap of the probe and titanium alloy front. It is considered that the insufficient stirring due to inclined side of the probe was contributed to the decrease of weld strength. After tensile test, fracture surface was analyzed by SEM. In the probe root area, dimples of Al were observed. In the probe tip area, the initial surface of titanium alloy plate was observed. However, in the middle area, similar amount of Ti and Al was detected. As result, it was confirmed that the fracture sequence was very complex and the fracture position was different according to the probe position.
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  • Tomo Ogura, Keisuke Ueda, Yuichi Saito, Akio Hirose
    2011 Volume 52 Issue 5 Pages 979-984
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 20, 2011
    JOURNALS FREE ACCESS
    Nanoindentation measurements were successfully applied to the interfacial reaction layers in dissimilar metal joints of 6000 series aluminum alloys containing alloying elements to steel in order to characterize their mechanical properties. The nanoindentation hardness of the reaction layer formed at the aluminum side was lower than that formed at the low carbon steel (SPCE) side of the investigated joints. At the aluminum side, the nanoindentation hardness changed by the addition of alloying elements. The hardness of the resulting Al12Fe3Si intermetallic compound (IMC) (and the same IMC containing Cu) was lower than that of Al3Fe. In comparison with the hardness values obtained from bulk Al-Fe binary series IMCs, it is considered that hardness changes of interfacial reaction layers are derived from the crystal structural changes produced by the alloying elements. The result of micro-testing of Al-Fe series IMCs indicates that the modification of the interfacial reaction layer by alloying elements contributes to higher ductility and the improvement of joint strength through crystal structural change.
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  • Sergio T. Amancio-Filho, Ana P. C. Camillo, Luciano Bergmann, Jorge F. ...
    2011 Volume 52 Issue 5 Pages 985-991
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    Friction Spot Welding (FSpW) is a new solid-state joining process able to produce similar and dissimilar overlap connections in different classes of materials. Advantages of this new technique are: short production cycles, high performance joints, absence of filler materials and good surface finishing supported by material refilling in the spot area. Although few authors have addressed the microstructural and mechanical behavior of friction spot welds of Aluminum alloys, there is still a lack of a systematic evaluation on the process-properties relationship. In this work the AA2024-T3 alloy (rolled sheets) was selected for the welding procedure. Design of Experiment and Analyses of Variance techniques were employed to evaluate joint shear strength under static loading. Sound joints with elevated shear strength were achieved and the influence of the main process parameters on joint strength evaluated.
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  • Shinji Kumai, Keisuke Hayashida, Mitsuhiro Watanabe
    2011 Volume 52 Issue 5 Pages 992-998
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: March 30, 2011
    JOURNALS FREE ACCESS
    Cylindrical 2024-T3 aluminum alloy studs were welded to 5052-H34 aluminum alloy plates by using an advanced high-speed solid-state joining method. Double cylindrical copper tubes, an assembly consisting of an inner tube and an outer tube, were used as electrodes. A stud having a circular ridge projection at its bottom was mounted at the end of the inner tube. The stud was then pressed against the plate surface. A discharge current was next introduced to the stud through the inner tube, whereupon the current flowed through the plate surface to the outer tube, which acts as a ground. The welding was completed within a few milliseconds without a notable increase in temperature of the joint. Subsequent examination revealed that the circular ridge projection had crushed and spread along the plate surface. Asymmetrical deformation occurred on both the inner side and outer side of the projection. The deformed area on the inner side of the projection consisted of a compacted grain structure. In contrast, the deformed area on the outer side exhibited a refined grain structure. These results indicate that the outside region was subjected to a higher temperature than the inside region. The joint was next investigated by tensile testing to evaluate its strength. The fracture surface of the joint region on the inner side of the projection exhibited a relatively flat surface with a limited number of dimples. On the other hand, that on the outer side was entirely covered with small dimples. Fracture stress was calculated by dividing the measured tensile fracture load by the dimple fracture area. The fracture stress thus obtained was found to be equivalent to the UTS of 5052-H34 alloy.
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  • Ji-Yeon Shim, Ill-Soo Kim, Moon-Jin Kang, In-Ju Kim, Kwang-Jin Lee, Bo ...
    2011 Volume 52 Issue 5 Pages 999-1002
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    Magnetic Pulse Welding (MPW) is not only one of the most useful welding processes for the dissimilar metal joining which uses cylindrical materials such as a pipe, but also a new technology for metal welding by means of repulsive force on account of the interaction between magnetic part of working coil and current induced in an outer pipe. Since the factors effected on quality of MPW are the charged voltage, the gap between inner pipe and outer pipes and a thickness of an outer pipe, the this study was focused on the investigation of the effect of process parameters and development of the mathematical model for the prediction on a quality of joint using Response Surface Method (RSM). To achieve the objective, the MPW equipment manufactured by WELDMATE CO., LTD. has been employed and applied for the materials such as the Al 1070, SM45C for Al and steel pipe respectively. After the sequent experiment, leakage test has been done to verify efficiency of the welding. The experimental values have been shown the good agreement with the predicted ones, indicating suitability of mathematical model employed. It is concluded that the gap between outer pipe and inner rod is one of major process parameters for influence on quality of joint while Al/steel pipe welding using the MPW.
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  • Shougo Kakizaki, Mitsuhiro Watanabe, Shinji Kumai
    2011 Volume 52 Issue 5 Pages 1003-1008
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 20, 2011
    JOURNALS FREE ACCESS
    Metal jet emission and weld interface formation in impact welding were investigated for similar- and dissimilar-metal lap joints. Numerical simulation of oblique collision between metal plates was performed using smoothed particle hydrodynamics (SPH) method for various plate thicknesses, collision velocities, and collision angles. Metal jet emission and formation of the characteristic wavy weld interface in impact welding were reproduced successfully. The composition of the metal jet was governed by the degree of relative density difference between two metals. When the density difference was large, such as Al/Cu and Al/Ni lap joints, the metal jet was mainly composed of the metal component with lower density, Al. On the other hand, when the density difference was small or zero, such as for Cu/Ni and Al/Al lap joints, the metal jet was composed of both metal components. Several types of lap joints were fabricated by magnetic pulse welding (MPW). Metal jets emitted from Al/Cu and Cu/Al lap joints were collected, and their components were analyzed by X-ray diffraction. The microstructure of the weld interface was also examined. The experimental results were in good agreement with the simulation results.
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  • Kaichi Saito, Akira Yasuhara, Masahiko Nishijima, Kenji Hiraga
    2011 Volume 52 Issue 5 Pages 1009-1015
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    Phase transformation of solid solution decomposition occurring in a 96 at%Mg-4 at%Dy alloy, which was solution-treated at 540°C and subsequently aged at 250°C for various lengths of time, has been investigated by conventional transmission electron microscopy (TEM) in combination with high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). The atomic-scaled observations based on both techniques provide the evidence that the first appreciable change in microstructure caused by aging is the occurrence of a short-range ordered state in Dy-segregated regions and that the short-range ordered state allows full of the nuclei of β′ phase associated with an Mg7Dy-type structure to occur in the domains, just as in cases of Mg-Gd and Mg-Y systems. With an increase of age-hardening effect, the β′ precipitates become larger and increasingly anisotropic in morphology, accompanying three orientation variants in coherent with the Mg-matrix. When reaching at the stage of hardness maximum (as-aged at 250°C for 100 h), the β′ precipitates, which have an orthorhombic structure with lattice parameters of a=0.659 nm, b=2.231 nm, c=0.523 nm, take the form of a thin disk-shape with a thickness of 20∼100 nm and a diameter of 200∼400 nm. With an advance of over-aging effect, the β′ precipitates are gradually reduced in volumes and replaced by β precipitates of cubic structure.
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  • Osvaldo Agustin Lambri, José Angel García, Werner Riehem ...
    2011 Volume 52 Issue 5 Pages 1016-1025
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    The mobility of dislocations has been investigated in WE43 magnesium alloy during recovery and recrystallisation for samples deformed plastically, at different degrees of plastic deformation and temperatures. The dislocation density decreases within the temperature range 550 K–650 K, in good agreement with the characteristic recovery temperature of this alloy, 630 K. New dislocations located at the grain boundaries start their movement from 650 K onwards. During recrystallisation, which has a characteristic temperature of around 700 K, the density of dislocations decreases and the possibility of movement of the dislocations also decreases, due to the development of internal stresses during the growth of new strain-free grains.
    The excess of vacancies promoted by the plastic deformation in cold worked samples is consumed up to temperatures of 550 K. New thermal vacancies which assist the movement of grain boundaries and dislocations are created after annealing at temperature above 650 K. Hot worked samples which exhibit dynamic recovery or recrystallisation, depending on the degree of plastic deformation; have a structure with both a scarce dislocations mobility and also a small dislocations density.
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  • Hitoshi Yamaguchi, Hisao Kikugawa, Takashi Asaka, Hirakazu Kasuya, Mas ...
    2011 Volume 52 Issue 5 Pages 1026-1032
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    Bone fracture toughness has been well studied, however, it is also important to investigate the effect of preservative treatment on the mechanical properties of bones. It is necessary to evaluate crack initiation and propagation after fracture because this process may be different in the case of injured bone tissues. In this study, we attempted to analyze the strain distribution on bone tissue surface by using image correlation techniques in order to elucidate the relationship between microscopic bone damage and strain distribution. Bovine femoral cortical bone was employed as the bone specimen and the three-point bend test method was used to determine the fracture toughness, in accordance with the ASTM E399 guidelines. An Instron type machine was used in the fracture toughness test and the loading rate was set to 1 mm/min. Black and white spray paint was applied in a random pattern to the surface of the specimens, and the specimens were loaded until they were ruptured. Bone surface strain analysis was performed using image correlation techniques and the changes were recorded in a digital image. In order to evaluate the effects of preservative treatment on the mechanical properties of bone, we categorized the specimens into 4 groups: the control group included the specimens that were submitted for testing immediately after machining and the preservation group comprised specimens that were analyzed after preservative treatment with different method (formalin, ethanol and physiological saline solution). A strain analysis performed using image correlation techniques allowed the visualization of the increased strain at the forward end of the slit of the specimens. The strain value at the forward end of the slit (the longitudinal direction of specimens) measured at the time of rupture in the control group was approximately 4 times larger than that in the formalin preservation group, thereby suggesting the embrittlement of bone organic constituents due to preservative treatment.
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  • Yuji Kurata, Hidetomo Sato, Hitoshi Yokota, Tetsuya Suzuki
    2011 Volume 52 Issue 5 Pages 1033-1040
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    A new Al-alloy coating method using Al, Ti and Fe powders has been applied to 316SS in order to develop corrosion resistant coating in liquid lead-bismuth eutectic (LBE). The 316SS plates with coating layers of different Al concentrations were exposed to liquid LBE with controlled oxygen concentrations of 10−6 to 10−4 mass% at 823 K for 3600 ks. While surface oxidation and grain boundary corrosion accompanied by liquid LBE penetration are observed in 316SS without Al-alloy coating, the Al-alloy coating is effective to protect such severe corrosion attacks in liquid LBE. Although the coating layer containing 2.8 mass% Al does not always keep sufficient corrosion resistance, good corrosion resistance is obtained through the Al-oxide film formed in liquid LBE in the coating layer where the average Al concentration is 4.2 mass%. Cracks are formed in the coating layer containing 17.8 mass% Al during the coating process. The Al-powder-alloy coating applied to 316SS is promising as a corrosion resistant coating method in liquid LBE environment.
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  • Makoto Hino, Yutaka Mitooka, Koji Murakami, Kazuto Urakami, Hiroyuki N ...
    2011 Volume 52 Issue 5 Pages 1041-1047
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    Laser joining for different materials between 1050 aluminum alloy sheet of 1 mm thickness and polypropylene sheet of 2 mm thickness using a newly developed insert sheet was studied. The diode laser-irradiation to the polypropylene side was carried out in air. The effects of the aluminum surface state on the joining properties were examined. The joining strength increased with the increase in aluminum surface area except for the surface with the intense ruggedness. It was found that the chemical condition of aluminum surface treated with the acid or alkaline solution strongly affected the joining strength rather than the surface roughness.
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  • Yoshihiro Sekiguchi, Yamato Hayashi, Hirotsugu Takizawa
    2011 Volume 52 Issue 5 Pages 1048-1052
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    Palladium nanoparticles were synthesized in the solid–liquid system of palladium oxide–alcohol by microwave irradiation. They were compared with those produced by a conventional heating method. We also used various alcohol solvents and compared the products obtained. The products contained particles that had diameters of several nanometers. In these measurements, microwave heating produced smaller particles than conventional heating because it provided homogeneous and direct heating. Additionally, Pd/spherical carbon (SC) composite particles could be prepared by the same method. For microwave heating, SC particles can support palladium particles without calcination, which is due to selective heating by microwaves.
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  • Sanghwan Lee, Bonghwan Kim, Sangmok Lee
    2011 Volume 52 Issue 5 Pages 1053-1062
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 20, 2011
    JOURNALS FREE ACCESS
    The effects of Fe content and cooling rate on the solidification path and formation behavior of the Al5FeSi (β) phase in Fe-containing hypoeutectic Al-Si alloys were studied based on thermodynamic analysis and pertinent experiments. The thermodynamic calculations were performed using the Thermo-Calc program. For analyses in the high alloy region of the Al-Si-Fe ternary system, a thermodynamic database for Thermo-Calc was correctly updated and revised by the collected up-to-date references. For thermodynamics-based predictions of the solidification path in Fe-containing hypoeutectic Al-Si alloys, liquidus projection (including various invariant, monovariant, and bivariant reactions and isotherms) and equilibrium phase fraction were calculated as functions of composition and temperature in the Al-Si-Fe ternary system. The calculated results were compared to experimental results using various casting runs. In order to analyze the solidification path as a function of Fe content, two representative hypoeutectic Al-Si alloys with different Fe levels were designed. To better understand the influence of cooling rate on the formation behavior of the β phase, the two alloys were solidified under slowly- and rapidly-cooled conditions, respectively. The cooling curves of the solidified alloys were recorded by thermal analysis and various important solidification events were detected using the first derivative of the cooling curves. Microstructures of the casting samples were studied by combined analyses of optical microscopy (OM) and scanning electron microscopy (SEM). For the slowly-cooled condition with the high Fe level, the primary β phase enveloping the Al8Fe2Si (α) phase was mainly formed by the quasi-peritectic reaction of L + α → (Al) + β (612°C). For the rapidly-cooled condition with the high Fe level, the primary β phase with morphology of a curved needle was mainly formed by the reaction of L → (Al) + β (579∼612°C).
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  • Jae Woo Ahn, Dong Wha Chung, Ki Woong Lee, Jong-Gwan Ahn, Hong Yong So ...
    2011 Volume 52 Issue 5 Pages 1063-1069
    Published: May 01, 2011
    Released: May 01, 2011
    JOURNALS FREE ACCESS
    Nitric acid leaching of waste plasma display panel (PDP) electrode scrap was investigated as a part of development for a pre-treatment process to increase Ru content in the scrap. Leaching performance was evaluated in terms of different experimental parameters such as nitric acid concentration, reaction temperature and time.
    An aqueous nitric acid leaching solution with a concentration range of 1.5 M–3.0 M at 60°C and 1.5 M–4.2 M at 75°C demonstrated as the most effective condition for the selective removal of Pb and Ba from waste PDP scrap powders with about 90% of Pb and 95% of Ba leached in 30 min. The rate of dissolution decreased after a certain level of HNO3 concentration due to formation of Pb(NO3)2 which has limited solubility in the aqueous solution. Other impurities such as Bi, Zn, Ag and Co were dissolved at the level of 75%–90% at all the leachant concentrations, leaching time and temperatures applied, while Si, Al and Fe showed a poor leachability with only 7%, 30% and 40% dissolution, respectively. Ru and Zr were almost insoluble in an aqueous nitric acid solution. The total concentration of Ru in the undissolved residue (27.96%) of the scrap powder after nitric acid leaching was brought up to 93.8% from the initial concentration (14.43%) of the scrap in the final process. The precipitation behavior of Pb(NO3)2 as well as the solubility of SiO2 were also investigated.
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  • Kuk Hyun Song, Han Sol Kim, Won Yong Kim
    2011 Volume 52 Issue 5 Pages 1070-1073
    Published: May 01, 2011
    Released: May 01, 2011
    [Advance publication] Released: April 13, 2011
    JOURNALS FREE ACCESS
    The aim of this work was to evaluate the effects of strain rate on the microstructural evolution of 5-mm-thick pure copper (99.99%) sheets subjected to conventional rolling (CR) and cross-roll rolling (CRR). The sheets were cold-rolled with a reduction ratio of 90% and then annealed at 400°C for 30 min to obtain the fully recrystallized microstructures. The resulting cold-rolled and annealed sheets had considerably finer grains than the initial sheets. In particular, the average grain size became smaller by CRR (6.5 μm) than by CR (9.8 μm). The mechanical properties of the sheets, i.e., Vickers microhardness and tensile strength, were more enhanced by CRR than by CR. The microstructural development in these processes was systematically discussed.
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