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Volume 46, Issue 3
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RESEARCH REPORT
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Shuu KURODA, Takeshi ITAGAKI, Ken TOHMA1996 Volume 46 Issue 3 Pages 113-118
Published: 1996
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSTo investigate localized corrosion characteristics of Al–Si alloy brazing filler, electrochemical measurements as well as immersion corrosion tests were carried out. Selective dissolution of eutectic phase occurred in the filler after brazing. On the other hand, no selective dissolution occurred in the filler with solution heat treatment after brazing. Pitting potential increased with increasing Si content in solid solution. Though cathodic reaction rate increased with an increase in Si content of the filler, the effect of Si itself was rather small. It was concluded that the localized corrosion of filler is caused by smaller Si content in solid solution at eutectic than that at primary α phase, and that matrix/Si particle interface acts as a more active cathode than matrix and Si particle.View full abstractDownload PDF (958K) -
Shoichi HIROSAWA, Tatsuo SATO, Akihiko KAMIO, Kazunori KOBAYASHI, Tosh ...1996 Volume 46 Issue 3 Pages 119-125
Published: 1996
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSThe age-hardening behavior and precipitation microstructures of Al–Li–Cu–Zr alloys containing various additional elements (Ag, Ge, Zn, Si, Mg and Mg+Ag) were investigated using hardness measurement and transmission electron microscopy. The experimental results indicate that the addition of Mg has a pronounced effect to produce a high density of T1 (Al2CuLi) phase at aging temperatures above ~400 K, resulting in the increased hardness of the alloys. In contrast, the additions of Ag, Ge, Zn and Si to the quaternary alloy exerts no marked influence on the precipitation kinetics. Difference in quenching condition, W.Q. (water-quench), D.Q. (direct-quench) or S.Q. (step-quench), strongly affects the precipitation microstructures and hardness of the alloys. This is well explained by taking into account the effects of both the quenched-in excess vacancies and Mg atoms. The proposed mechanism is that the excess vacancies aggregate together with Mg and Cu atoms to form Mg/Cu/Vacancy complexes which play an important role in the enhanced nucleation of the T1 phase (Mg/Cu/Vacancy complex mechanism).View full abstractDownload PDF (965K) -
Jianguo HU, Keisuke IKEDA, Tadasu MURAKAMI1996 Volume 46 Issue 3 Pages 126-131
Published: 1996
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSEffects of heat treatments after hot-rolling on subsequent cold-rolling and annealing textures, and formability for 5083 alloy sheets were investigated by means of pole figures measured with X-ray, uniaxial tension, plane strain tension, bulging and deep drawing tests. The influence of the temperature of the heat treatment on precipitation and recrystallization during subsequent annealing after cold-rolling was analysed using transmission electron microscopy and Vickers hardness tests. The following conclusions were obtained: Heat treatments after hot-rolling can make texture components {123}<634> and {112}<111> become stronger, especially for the latter. They also cause {110}<112> to become weaker during the subsequent cold-rolling. During annealing above the recrystallization temperature, the heat treatments can produce a mixed texture with both stronger {112}<111> and {100}<001>, and weaker {110}<112> components. The mixture of textures has caused the limit diameter ratio of deep drawing to increase and in-plane plastic anisotropy to decrease. The improvement of formability of the alloy sheets is ascribed to both the increase of solid solution of Mn and Mg and the decrease of precipitates caused by the heat treatments after hot-rolling, and also to the evolution of textures on subsequent cold-rolling and annealing.View full abstractDownload PDF (1162K) -
Masanori TSUNEKAWA, Norifumi HAYASHI, Teruo UNO1996 Volume 46 Issue 3 Pages 132-137
Published: 1996
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSOptimization of the secondary cooling conditions for aluminum DC slab casting is very important because they have a strong effect on the castability and the quality of slabs. The cooling capacities were evaluated by measuring the aluminum block temperature under various cooling conditions. The heat transfer coefficients were calculated with various factors changed. Those factors are the quality of block alloys, cooling surface conditions, amount of water fluxes, water temperatures, water impingement angles, mold lubricant mixing content, and CO2 gas mixing content. On the basis of the experimental data, the effects of above factors on heat transfer coefficients were quantified. For example, as the water temperature increased every one degree, heat transfer coefficient decreased about 1%, and as the mold lubricant mixing content to cooling water increased every 50 ppm, the coefficient decreased about 1%. It became clear that all cooling factors studied in the present work had a seriously influence on cooling capacities.View full abstractDownload PDF (851K) -
Keizo SAKURAI, Katsushige ADACHI, Toshiaki KAMEKAWA, Koichi OGAWA, Shi ...1996 Volume 46 Issue 3 Pages 138-143
Published: 1996
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSWhen drilling a titanium alloy, its low heat conductivity causes slow dispersion of heat evolved as a result of friction with a drill. Then a significant build up of heat at the cutting edges occurs, resulting in the increased welding phenomenon of chips at the tool flank as well as increased chipping. Therefore, it becomes difficult to determine a suitable cutting condition and tool material. In this work, intermittently decelerated feed drilling tests with high speed steel drills for a Ti–6%Al–4%V alloy were carried out on a CNC machine tool to improve the rate of chip removal. The results show the formation of easy-to-eliminate chips, reduced chip clogging, increased chip removal. Consequently, heat is readily dispersed to the exterior and the build up of heat at the cutting edges is reduced, resulting in the increased tool life by two times over a conventional drilling. Intermittently decelerated feed drilling is an effective method in drilling titanium alloys.View full abstractDownload PDF (953K) -
Hiroshi OHUCHI, Yukio KANAYAMA, Tsuyoshi IRISAWA1996 Volume 46 Issue 3 Pages 144-149
Published: 1996
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSAl–Si–X alloy castings are generally used for the parts subjected in thermal environment; for example, automobile engine's piston and cylinder. One of desirable properties for such parts is the littleness of thermal deformation (contour change and surface cracking). In this study, the effect of Cu, Mg contents on cyclic thermal shock (T/S) properties of Al–12% Si alloy castings is investigated from viewpoints of plastic deformation and microstructure. Specimens were subjected under cyclic T/S of rapid cooling in ice water to 500 cycles, and the changes of deformation and specific gravity were measured every 100 cycles. The main result obtained in this study is that about 1% addition of Cu or Mg contributes the cyclic T/S improvement.View full abstractDownload PDF (898K) -
Naohisa NISHINO, Shin-ichi TOWATA1996 Volume 46 Issue 3 Pages 150-155
Published: 1996
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSThe effect of heat treatment on interfacial reaction and the tensile properties were investigated on aluminum-borate whisker reinforced age-hardenable Al–Cu–Mg–Si and Al–Cu–Si alloys. In the Al–Cu–Mg–Si alloy matrix composites, fine reaction products were formed at the whisker surfaces during solution heat treatment, which were identified to be MgAl2O4. These reaction products caused the brittle fracture of the composites by notch effect. In addition to the deterioration of whisker by the interfacial reaction, the comsumption of magnesium in the matrix led to a change of precipitation behavior. Then, Al–Cu–Mg–Si alloy matrix composites lost the age-hardenability. Therefore, the tensile strength of the T6 treated aluminum-borate whisker reinforced Al–Cu–Mg–Si alloy was similar to that of the unreinforced aluminum alloy. On the other hand, the tensile strength of the heat treated magnesium-free Al–Cu–Si alloy matrix composites was higher than that of the unreinforced aluminum alloy.View full abstractDownload PDF (772K)
LECTURE
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Toshio SUZUKI1996 Volume 46 Issue 3 Pages 156-161
Published: 1996
Released on J-STAGE: February 15, 2022
JOURNAL FREE ACCESSDownload PDF (5294K)
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