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Volume 42, Issue 12
Displaying 1-24 of 24 articles from this issue
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M. Ö. Pekgüleryüz, M. M. Avedesian1992 Volume 42 Issue 12 Pages 679-686
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
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Kazuo TAKASHIRO1992 Volume 42 Issue 12 Pages 687-698
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
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Tsuneo SAGA1992 Volume 42 Issue 12 Pages 699-706
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
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Tadao ITO, Hidetomo SHIRAI1992 Volume 42 Issue 12 Pages 707-719
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
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Toshiyuki SATO, Junichi KANEKO, Makoto SUGAMATA1992 Volume 42 Issue 12 Pages 720-726
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSRapidly solidified flakes of Mg-6mass%Zn alloys with addition of Zr, Mn, Ni, Si and Ce were produced by argon gas atomization and subsequent splat quenching onto a water-cooled copper roll. Consolidation of the flakes was done by cold pressing and hot extrusion at a reduction of 25:1. The solidified flakes show fine dendritic cell structures with cell size of 1 to 2μm. Fine grained structures are observed in the extruded P/M materials. Although age hardening is greatly reduced, the Ce-bearing alloy shows the highest hardness among the tested alloys in as rapidly solidified and as-extruded conditions. The as-extruded material of Ce-bearing alloy shows the highest tensile strength of 554MPa at room temperature and hence higher specific strength than T6-treated Ti-6Al-4V alloy. It also shows high tensile strength of 188MPa at 473K. However, all the P/M materials showed lower tensile strength as well as higher elongation at 573K than the I/M material of Zr-bearing alloy.View full abstractDownload PDF (1883K) -
Shigeharu KAMADO, Shigeru IWASAWA, Kiyoaki OHUCHI, Yo KOJIMA, Ryuuji N ...1992 Volume 42 Issue 12 Pages 727-733
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSMagnesium alloys with Gadolinium or Terbium, whose content 20mass% was near the maximum solid solubility, were melted by means of a fluxless method and their age hardening behavior, mechanical properties at elevated temperature and physical properties were investigated. Both alloys exhibit considerable age hardening and the age hardening playes an important role for strength of Mg-Gd alloy even at 573K. Hardness of the aged specimens decreases steeply with rise of temperature beyond 473K, whereas that of the solution-treated Mg-Gd alloy shows positive dependence on temperature up to 573K, which is considered to be probably due to the precipitation. Tensile strength increases as temperature increases and reaches the maximum strength at 523K, namely 320MPa for Mg-Tb alloy and 330MPa for Mg-Gd alloy. The values are far superior to those of the conventional heat-resistant magnesium and aluminum alloys. Elongation of the aged specimens is less than 1% below 473K, but above that it increases in accordance with a change of fracture mode from transgranular to intergranular fracture with increasing temperature. Density of both alloys is three quarter of conventional aluminum alloys. As compared with practical magnesium alloy, their density is about 15% bigger, thermal conductivities are superior, but coefficients of thermal expansion is higher somewhat.View full abstractDownload PDF (1725K) -
Shigeharu KAMADO, Akira YUASA, Takahisa HITOMI, Yo KOJIMA1992 Volume 42 Issue 12 Pages 734-740
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSAZ91D magnesium alloy was directly heated to mushy zone from room temperature without melting and was stirred at constant temperature, 858K, for 7.2ks. Effects of stirring conditions and the fineness of raw materials on microstruc- tural changes, behavior of apparent viscosity during isothermal stirring and macrostructures after the stirring were investigated. Microstructures of stir-cast AZ91D alloy consists of primary α phase and fine eutectic phase created by a rapid cooling after the stirring. Morphology of α phase changes from slender form to spheroid with the elapse of the stirring time. When raw material with large grains is stirred with a paddle-type stirrer, the spheroidization of α phase becomes faster and its size becomes smaller as stirring rate increases. But in the case of an attritor-type stirrer, the size of α phase increases with increase of stirring rate owing to acceleration of the coalescence of grains. The size of α phase decreases with decrease in fineness of microstructure of raw material. A rapid reduction of stirring torque is probably caused by decrease of solid fraction and the spheroidization of α phase at an initial stage of the stirring. Thereafter, stirring torque gradually decreases, corresponding approximately to the spheroidization of α phase. Based upon the results of a visualized experiment for fluid flow during the stirring by utilizing glycerin at 285K, it is found that the entrapping of gas into specimen can be prevented by increasing metal head.View full abstractDownload PDF (2710K) -
Shotaro MOROZUMI, Manabu MATSUMOTO, Hiroshi SAIKAWA, Tomoya MINEGISHI, ...1992 Volume 42 Issue 12 Pages 741-746
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSBeing mixed with magnesium powder by up to 50%, 304 stainless steel and titanium powders were compacted under various compacting loads, respectively, and then the green compacts were sintered in a vacuum of 10-2Pa, finally at 1375K where magnesium can be vaporized completely. The sintered compacts were examined as to density, compressive strength and structure. The density and compressive strength decreased with increase in the amount of magnesium powder added to the green compacts, as well as decrease in the compacting load. The process was applied to make sintered ZrNi compacts capsulated with porous sintered stainless steel compacts. Sintered titanium and nickel compacts with a graded porosity distribution were also prepared, respectively.View full abstractDownload PDF (1879K) -
Tsuneo SAGA, Kazuo MATSUZAWA, Shuji NAGAI, Makoto OGAWA1992 Volume 42 Issue 12 Pages 747-751
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSEffects of drill's width of margin and back taper on the deep drilling of AZ31 magnesium alloy bars have been investigated. The reduction of drill's width of margin produced remarkable effects such as the improved chip discharge, the reduced cutting resistance, the significantly improved machined surface and the restrained outlet burr creation. These effects enabled the drilling into deeper parts easily. The similar effect was also obtained by giving back taper to a drill. To conclude, the reduction of drill's width of margin as well as back taper given to a drill are extremely effective to improve both the safety in drilling and drill's tool life.View full abstractDownload PDF (1215K) -
Fumihiro SATO, Yoshihiko ASAKAWA, Takenori NAKAYAMA, Hiroshi SATOH1992 Volume 42 Issue 12 Pages 752-758
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe effect of surface treatment on the corrosion behavior of diecast magnesium alloy AZ 91D-F has been investigated by salt spraying test. It was found that the corrosion resistance of the alloy decreased in the following order of surface treatments: anodizing with sealing, chromating, anodizing without sealing, mechanical polishing and no treatment (as-cast). In any case, both the weight loss and the estimated maximum corrosion depth increased linearly with increase in the duration of spray test. X-ray diffraction analysis revealed that corrosion products consisted mainly of Mg(OH)2 and NaCl, irrespective of surface treatments. Polarization characteristics in 5%NaCl aqueous solution, however, depend on the surface states and are correlated well with the order of corrosion resistance.View full abstractDownload PDF (1890K) -
Yoshihiko ASAKAWA, Fumihiro SATO, Takenori NAKAYAMA, Hiroshi SATOH1992 Volume 42 Issue 12 Pages 759-764
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSCorrosion behavior of sand-casted Mg-(0-5.3%)Al and Mg-5.3%Al-(0-2.7%) Zn alloys have been investigated by salt spraying test (SST). The corrosion resistance increased with an increase of Al content in Mg-Al alloys, and more than 1% content of Zn in Mg-5.3%Al-Zn alloys. These behavior were seemed to depend on the volume fraction of nodule structure. Cross-sectional microstructure after corrosion test showed that the matrix was preferentially attacked and the nodule structure was more resistant to corrosion. These dependence of corrosion resistance on the nodule content was discussed from the view point of galvanic effect between the nodule structure and the matrix, and barrier effect of the nodule structure.View full abstractDownload PDF (1227K) -
Shinji ANDO, Kanji NAKAMURA, Kazuki TAKASHIMA, Hideki TONDA1992 Volume 42 Issue 12 Pages 765-771
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSMagnesium single crystals were stretched in [1120] direction to investigate the deformation behavior by {1122} <1123> slip (SPCS). In a range from 77K to 133K, the yield stress decreases with increasing temperature, while the stress increases with increasing temperature in a range from 133K to 293K. The stress increases at all temperatures when strain rate is increased by a factor of a hundred. The deformation mode due to SPCS is investigated by observation of slip band. Narrow slip bands are formed at 77K just after yielding. The width of slip bands at yielding increases continuously with increasing temperature and coveres the whole specimen surface at 293K. The results of the observation by TEM show that double cross slip of (c+a) screw dislocations occurrs more frequently during deformation at 293K than at 77K. At 293K, there are scarcely (c+a) edge dislocations, while many c edge dislocations are observed in the crystals. The deformation mode and the deformation mechanism of magnesium by SPCS are similar to those of cadmium.View full abstractDownload PDF (2190K) -
Suk-won LIM, Takao CHOH1992 Volume 42 Issue 12 Pages 772-778
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSTiC particulate reinforced magnesium matrix composites were fabricated by melt stirring method. The effect of alloying elements on TiC particulate dispersion into molten magnesium and mechanical properties were investigated. The incorporation time is defined as the time required for dispersion of solid particles into molten metal. The incorporation time of TiC particles into molten pure magnesium was remarkably shorter and the particulate dispersion was more uniform than that of pure aluminum which was reported previously. The incorporation time was prolonged by the addition of Al, Bi, Ca, Ce, Cu, Pb, Sn or Zn. The tensile strength increased and elongation decreased by the addition of Cu or Sn into the matrices and composites. Although, the tensile strength of the matrices and composites increased by alloying with Ca or Ce, the maximum elongation was observed at a content of about 1% for the matrices. By alloying with Zn, the tensile strength increased for the matrices and composites, but the elongation of the matrices increased. The pure magnesium and its alloy matrix composites reinforced with 20vol%TiC have the tensile strength of about 400MPa. This value is compared with the tensile strength of SiC whisker reinforced magnesium matrix composites fabricated by liquid infiltration method at the same volume fraction. Therefore, the melt stirring method which has the advantages of simple process is considered to be efficient in fabricating magnesium matrix composites.View full abstractDownload PDF (2771K) -
Kazuo MATSUZAWA, Shuji NAGAI, Tsuneo SAGA, Yo KOJIMA1992 Volume 42 Issue 12 Pages 779-783
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe effect of Li content on the cutting mechanism of Mg-Li-1mass%Al alloys containing 5, 8 and 16mass%Li has been investigated by both cutting force measurements under orthogonal cutting and microscopical observation. The magnitude of the cutting force increased with increasing the additional element of Li, and was found to change in the order of rake angle, π/18>π/9>π/6 rad. The estimated shear angle from cutting ratio decreased with increasing Li content. The chip form and machined surface roughness indicated that the chip formation processes were a shear chip type cutting and a continuous chip type cutting for a 5%Li alloy and for 8 and 16%Li alloys, respectively. In the 16%Li alloy giving high cutting force, a crack located in front of tool tip was observed on the quick-stopped microstructure. This was explained by the fact that the grain size of the 16%Li alloy was not fine enough compared with the depth of cut.View full abstractDownload PDF (1300K) -
Matsufumi TAKAYA, Tetsuzi ITOH, Hiroyuki UMEHARA1992 Volume 42 Issue 12 Pages 784-789
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSAZ91 magnesium alloy die cast panels were produced using high purity magnesium. Both AZ91 magnesium alloys and ADC12 aluminum alloys die cast panels coated with the same kind of paint were tested in the salt spraying. The films for painting on AZ91 alloys were formed from various chemical conversion and anodic oxide baths, and the films on ADC12 alloys were formed from chromating. The composition of chemical conversion coatings were measured using Auger Electron Spectroscopy (AES). The painting on those panels were finished with the thermosetting acrylic resin after the thermosetting epoxy resin primer. The chromate and anodic oxide films were superior as under layer for painting on AZ91 alloys, the adhesion of painting and corrosion resistance showed same degree compared with coated ADC12 aluminum alloys.View full abstractDownload PDF (1602K) -
Hiroyuki SATO, Takahiro HAMADA, Hiroshi OIKAWA1992 Volume 42 Issue 12 Pages 790-796
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSCreep behavior of an extruded Mg-3 mol%Al solid solution alloy has been examined at 600 and 650K where the activation energy of creep is similar to that for diffusion. Compression creep tests were performed on longitudinal samples and transverse samples. Two types of creep behavior, termed "Alloy" and "Metal", were observed on both samples at lower and higher stresses, respectively. Stress exponent at the lower stress range is about 3, and 6 at the higher stress range. A change in the type of creep curves is observed at 650K. The creep characteristics and the transition stress from "Alloy" to "Metal" type depend on the stress direction so that the transition occurs at lower stress in transverse samples. These results are discussed in terms of the breakaway stresses from solute atmosphere on different slip planes.View full abstractDownload PDF (745K) -
Atsushi YAMAMOTO, Tetsuya ASHIDA, Harushige TSUBAKINO, Ryoichi NOZATO1992 Volume 42 Issue 12 Pages 797-803
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSPrecipitation behaviour of Mg-11%Li-10%Zn ternary alloy during aging between room temperature and 473K was investigated. Age-hardening phenomena was observed on aged specimens except at 473K. Metastable MgLi2Zn (θ') phase precipitated at a hardening stage. Stable α and θ phases were observed at an over-aging stage. By means of transmission electron microscopy (TEM), orientation relationships among matrix and θ', α and θ phases were determined as follows;
(011)β//(011)θ', [100]β//[100]θ'
(011)β//(0001)α, [111]β//[2110]α
(111)β//(112)θ, [110]β//[111]θ.
By the consideration of the orientation relationships and lattice constants of precipitates, it can be concluded that the increase in hardness during aging is due to the coherent strain between θ' and the matrix and that the decrease in hardness is a result of relaxing the strain by precipitation of α phase.View full abstractDownload PDF (1987K) -
Tatsuo SATO, Isao TAKAHASHI, Hiroyasu TEZUKA, Akihiko KAMIO1992 Volume 42 Issue 12 Pages 804-809
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSPrecipitation process and microstructures of both Mg-5%Y and Mg-10%Y (in mass%) alloys were investigated using hardness measurement, optical microscopy and transmission electron microscopy. In a Mg-5%Y alloy hardness increased slightly by about HV 10 with aging time at temperatures between 423 and 523K. In a Mg-10%Y alloy hardness increased markedly after certain incubation periods from 4340 to 38.7ks at aging temperatures between 423 and 498K. The TTT diagram for the precipitation of the β" phase was determined from the hardness curves of a Mg-10%Y alloy, the nose temperature being 498K. The hardness increase in a Mg-10%Y alloy at 423 to 498K was found to be caused by the homogeneous precipitation of the fine coherent metastable β" phase. The metastable β' and stable β phases precipitated and coarsened in a Mg-10%Y alloy at 523 to 573K. Both the β" and β' phases were found to have a base centered orthorhombic (bco) structure. The atom configurations in their unit cells, however, were assumed to be different from each other in the β" and β' phases because of the existence of weak reflection spots at the forbidden positions.View full abstractDownload PDF (3303K) -
Kunihiko MAKINO, Toshiro KAWATA, Hideo HANE1992 Volume 42 Issue 12 Pages 810-814
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
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Tadao ITO, Takanori TAKIKITA1992 Volume 42 Issue 12 Pages 815-821
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
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Shin-itiroh FUJIKAWA1992 Volume 42 Issue 12 Pages 822-825
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
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Shin-itiroh FUJIKAWA1992 Volume 42 Issue 12 Pages 826-827
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
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Makoto SUGAMATA1992 Volume 42 Issue 12 Pages 828-829
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
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1992 Volume 42 Issue 12 Pages 830-832
Published: December 30, 1992
Released on J-STAGE: October 30, 2008
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