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Volume 44, Issue 5
Displaying 1-11 of 11 articles from this issue
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Toshio HAGA, Mitsugu MOTOMURA1994 Volume 44 Issue 5 Pages 257-262
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSFactors which affect the sticking distance of Al-12mass%Si foil to the roll was investigated in this study. 4 kinds of roll (copper, brass, S45C, SUS304) were used. The roll speed was 1500rpm (24m/s) and 3500rpm (55m/s). The nozzle which had a 0.5 × 20mm rectangular slit was used to eject molten metal. The sticking distance of Al-12mass%Si alloy foil increases with roll temperature, which depends on the thermal conductivity of roll material. Wetting condition between the molten metal and the roll dosen't affect the sticking distance. The sticking distance is unrelated to the contacting area ratio between the foil and the roll, the roughness of roll and the temperature of molten metal.View full abstractDownload PDF (736K) -
Shogo TOMIDA, Kazuhiro NAKATA, Fukuhisa MATSUDA1994 Volume 44 Issue 5 Pages 263-268
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSAl-(25, 34, 46 and 50mass%) Cu filler rods were overlaid on 1070 aluminum plate by TIG welding under various currents. The hardness of overlaid layer with hypo-eutectic, eutectic and hyper-eutectic structures are HV100-160, HV180-220 and HV210-330, respectively. The reason why the hardness increase with increasing in Cu content is explained to be due to the increase of amount of eutectic in hypo-eutectic and the increase of amount of primary θ (CuAl2) in hyper-eutectic. The wear resistance of overlaid layer increases with the increase in hardness or Cu content, and it becomes to saturate to about 1/3 of that of base metal at more than HV200 or 30mass%Cu. In order to get this optimum overlaid layer the recommended welding condition is selected to get about 10% of dilution rate by using Al-Cu filler rod with more than 34mass%Cu.View full abstractDownload PDF (1681K) -
Isao KUBOKI, Yoshinobu MOTOHASHI, Mitsuji HIROHASHI1994 Volume 44 Issue 5 Pages 269-274
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSTensile tests for the Ti-15V-3Cr-3Sn-3Al alloys with different initial structures have been conducted by means of a constant cross-head speed method (constant method) and a cross-head speed jumping method (jumping method) at temperatures around the β transus. For specimens with relatively large grain sizes ranging between 15 and 170μm, the strain rate giving the maximum total elongation moves to higher values with decreasing grain size. Grain size exponent, p, in the Dorn equation for creep is about 0.5 for the present alloy, which is fairly small compared with the value of 2 or 3 usually obtained for the superplastic alloys with fine grains. The total elongation of the specimen with a dual-phase microstructure is always larger than that of the specimen with an equiaxial single-phase microstructure at temperatures below the β transus. The jumping method gives a better correlation between the m-value and the total elongation than the constant method. The total elongation becomes large when the m-value is fairly high and remains constant at a wider strain range.View full abstractDownload PDF (978K) -
Isao KUBOKI, Yoshinobu MOTOHASHI, Mitsuji HIROHASHI1994 Volume 44 Issue 5 Pages 275-280
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSMicrostructural evolution during tensile deformation of a Ti-15V-3Cr-3Sn-3Al alloy at temperatures around its β transus has been studied using transmission electron microscopy as well as optical microscopy. An increase in the misorientation angle between subgrains of the alloy in a β phase state is possibly due to the coalescence of the subgrains, which is followed by the continuous recrystallization without grain boundary migration. A superplastic-like phenomenon is observed not only in the alloys with fairly small initial grain size but also in the alloys with relatively large grain size, since a strain point where the onset of grain refinement occurs moves to a smaller strain point with decreasing the initial grain size. An increase in the elongation at temperatures below β transus observed for a cold-rolled alloy is due to the formation of the uniform microduplex structure containing very fine subgrains during deformation.View full abstractDownload PDF (1931K) -
Biing Hwa YAN, Min Der CHEN1994 Volume 44 Issue 5 Pages 281-285
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSA new method for improving the EDM (electrical discharge machining) performance of a Ti-6Al-4V alloy is investigated. The experimental results indicate that the best overall performance is achieved using ultrasonic vibration dielectric. The improvement mechanism is that the ultrasonic vibration results in the restraining of discharge concentration and the formation of small debris. It is also found to be effective for promoting the machined surface roughness to use ultrasonic vibration dielectric suspended with electrically conductive powder such as pure aluminum powder.View full abstractDownload PDF (1042K) -
Jingtao WANG, Minoru FURUKAWA, Zenji HORITA, Minoru NEMOTO, Yan MA, Te ...1994 Volume 44 Issue 5 Pages 286-291
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSExperiments were conducted on a composite material (Comral-85) fabricated by ingot metallurgy. The composite consisted of a 6061 aluminum alloy matrix and a reinforcement of 20 vol% Al2O3-based microspheres having an average diameter of 20μm. The age hardening behavior, temperature dependence of the yield stress and the creep behavior of the composite after extrusion were investigated and compared with those of 6061 aluminum alloy. In the as-quenched state, the yield stress of the composite is 40-85MPa higher than that of the 6061 alloy. This difference is attributed to the high density of dislocations within the matrix which are introduced by the difference in thermal expansion coefficients between the matrix and the reinforcement. The difference in yield stress between the composite and the 6061 alloy decreases with aging time and the age hardening curves for both materials have a similar trend. At room temperature, the strain hardening rate of the composite is higher than that of the 6061 alloy, probably because the distribution of reinforcement enhances the dislocation density during deformation. Both the yield stress and the strain hardening rate of the T6-treated composite decrease as the testing temperature increases, and the rate of decrease is faster in the composite than in the 6061 alloy. Under creep conditions, the stress exponents of the T6-treated composite vary from 8.3 at 473K to 4.8 at 623K. These exponents are larger than those of the 6061 matrix alloy.View full abstractDownload PDF (1486K) -
Keijiro NAKASA1994 Volume 44 Issue 5 Pages 292-297
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSFatigue tests were carried out on the preloaded notch-specimens of 7075-T6 aluminum alloy under stress ratio of 0.1 and frequency of 1Hz, and the fatigue crack initiation and propagation behaviors were investigated. The tensile preloading, which corresponds to 80% of fracture load, increases the crack initiation life, while the compressive preloading decreases the life. The effect of preloading is larger when the overload ratio, or the ratio of preload to maximum repeating load, is larger. Through a microarea X-ray analysis near notch root, the compressive residual stress is discovered to be generated by the tensile preloading and the maximum repeating stress at notch root is found to be decreased, which will be the main reason for the increase in fatigue crack initiation life. The crack propagation velocity after crack initiation from notch root is decreased or increased within the preload-affected zone by the tensile or compressive preloading, respectively.View full abstractDownload PDF (927K) -
Atsushi HIBINO, Masazumi OKIDO, Takeo OKI1994 Volume 44 Issue 5 Pages 298-304
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSRelation between pit morphologies and interfacial impedance characteristics was investigated on an aluminum foil with the (100) crystal orientation under a corrosion potential in 1mol•dm-3 hydrochloric acid solution. Effects of solution temperature, concentration of hydrochloric acid and addition of sulfuric acid on impedance parameters of charge transfer resistance, Rct, time constant, τ0 and reaction uniformity parameter, θ, were discussed. With increasing temperature and hydrochloric acid concentrations, the average of τ decreases and its distribution becomes wider. With addition of sulfuric acid, the average increases and the distribution becomes sharper. In this experiment, it is considered that τ0, which is the horizontal axis of distribution of reaction activity corresponds to the degree of aluminum dissolution, and the distribution density, which is the vertical axis corresponds to the surface uniformity. If we will choose such conditions that the τ0 value is below 1.0ms and the distribution density is below 0.7, etch pit sites are expected generated independently from each other without aggregation of many pit sites.View full abstractDownload PDF (1289K) -
Koichi OGAWA, Hiroshi YAMAGUCHI, Yoshiaki YAMAMOTO, Kenichi KITAURA1994 Volume 44 Issue 5 Pages 305-310
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSHigh strength aluminum alloy A7075 was friction welded under three forging pressures, while other friction welding conditions were kept constant throughout the welding cycle. Friction welded joints were offered to destructive test for evaluating the bending and torsional strength. The maximum joint efficiencies were 80.2, 98.4 and 104.8% in bending test, torsion test with smoothed specimen and that with notched specimen, respectively. In bending test and torsion test with notched specimen fracture occurred at the transition layer between the interfacial layer and the deformed zone of welded joints, while it occurred in softened zone near the transition zone in torsion test with smoothed specimen.View full abstractDownload PDF (1428K) -
Yoshitsugu MISHIMA1994 Volume 44 Issue 5 Pages 311
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (213K) -
Kazuo KATORI1994 Volume 44 Issue 5 Pages 312-313
Published: May 30, 1994
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (202K)
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