Journal of Japan Institute of Light Metals

Relation between drop of corrosion potential and concentration of chlorine ions in pits on Al-Fe alloys

Osami SERI, Kohsuke TAGASHIRA

1988 Volume 38 Issue 4 Pages 191-196
Published: April 30, 1988
Released on J-STAGE: July 23, 2008

DOIhttps://doi.org/10.2464/jilm.38.191

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An attempt was made to clarify a correlation between the concentration of Cl^- ions in pitting cavities and the drop of corrosion potential for Al-Fe alloys in natural environments containing chloride. The concentration of Cl^- ions in pits on Al-Fe alloys corroded in 0.1M NaCl aqueous solution moderately stirred with a magnetic mixer and aerated with an air pump is equivalent to that in 0.6 to 0.9M AlCl₃ aqueous solution.

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Superplastic deformation of Al-Ca-Zn eutectic alloys

Norio KOHNO, Takashi SAKUMA, Hisafuji WATANABE, Shigeo MUROMACHI

1988 Volume 38 Issue 4 Pages 197-201
Published: April 30, 1988
Released on J-STAGE: July 23, 2008

DOIhttps://doi.org/10.2464/jilm.38.197

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Effects of Zn in Al-Ca-Zn superplastic alloys and hot working temperatures were studied by means of tensile and microforming tests. The elongation at room temperature increases with increasing Zn, while the supperplasticity and microformability fall down to a lesser degree than those of Al-Ca binary alloys. It is attributed to a decrease in volume fraction of intermetallic compounds with increasing Zn as shown in the previous work of the present authors on the Al-Ca-Zn phase diagram. Al-5.6%Ca-2.1%Zn alloy is a prominent superplastic material. This alloy worked at 450°C is superior in superplastic deformation properties to that worked at 550°C. Because grain growth in the former delays during hot working.

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New solution treatment for Al-Si-Cu alloy castings at non-equilibrium eutectic melting temperatures

Yoshihiro SHIMIZU, Yoji AWANO, Motoyuki NAKAMURA

1988 Volume 38 Issue 4 Pages 202-207
Published: April 30, 1988
Released on J-STAGE: July 23, 2008

DOIhttps://doi.org/10.2464/jilm.38.202

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A new solution treatment was tried for Al-Si-Cu alloy castings in which practical castings were heated at temperatures between final solidification temperature and solidus temperature in the equilibrium phase diagram. When the practical castings containing non-equilibrium Cu bearing compounds were heated above the final solidification temperature, non-equilibrium eutectic areas containing the Cu compounds are remelted and rapidly decreased in area remaining little compounds. Both spherodization of eutectic Si and dissolution of non-equilibrium Cu bearing compounds are promoted by this treatment. Needle shape Fe bearing compounds are also refined. The castings solution-treated in this manner have impact strength extremely higher than those treated in the conventional one.

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Morphological effects of precipitates on fracture mechanism of high purity Al-Zn-Mg alloys

Eiji KATO, Yoshisada UEDA, Yasuyuki ARAKAWA

1988 Volume 38 Issue 4 Pages 208-215
Published: April 30, 1988
Released on J-STAGE: July 23, 2008

DOIhttps://doi.org/10.2464/jilm.38.208

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Microstructures of high purity Al-Zn-Mg alloys were controlled by Cr and Zr additions and different conditions of aging. The properly Zr-added alloys mainly fracture from the crack initiated at grain boundaries. The fracture toughness is determined by the size and distribution of grain boundary particles. This is attributed to that the fracture toughness is directly proportional to the area fraction of grain boundary particles, but not to the particles in the matrix and PFZ width. Cracking of the Cr-added alloys initiates at Cr dispersoids in the matrix. The fracture toughness of these alloys is proportional to the volume fraction of particles in the matrix, but not to the grain boundary particles and PFZ width. The PFZ width in the Cr-added and Zr-added alloys has no effect on the fracture toughness. The PFZ width may have an influence to crack propagation. Cr addition is superior to Zr addition in fracture toughness. The fracture mode of Cr-added alloys is transgranular, while that of the Zr-added alloys is predominantly intergranular.

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Effects of Si content and gas dissolution on shrinkage morphology of hypoeutectic Al-Si alloys

Kazufumi MORIMOTO, Hiroyuki TAKAMIYA, Yoji AWANO, Motoyuki NAKAMURA

1988 Volume 38 Issue 4 Pages 216-221
Published: April 30, 1988
Released on J-STAGE: July 23, 2008

DOIhttps://doi.org/10.2464/jilm.38.216

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Hypoeutectic Al-Si alloys vacuum degassed and gas enriched were cast into conical shell molds. The castings having different quantities of gas porosities show nearly the same total shrinkage volume which decreases at higher Si contents. Pure aluminum and Al-10%Si alloy permit an unchanged volume of external shrinkage and reduced volumes of internal shrinkage with an increase in porosity volume. Al-4%Si and Al-7%Si alloys permit unchanged volumes of internal and external shrinkages respectively at lower and higher porosity levels. The volumes of internal shrinkage at higher porosity levels and of external one at lower porosity levels decrease with an increase in porosity volume. The porosity changes from a concentrated type to dispersed one with an increase in porosity volume. The gas dissolved in the melt has remarkable effects on the shrinkage morphology.

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Consolidation of rapidly solidified Al-Si powders by the strained powder rolling method

Hidenobu GOHCHI, Kojiro F. KOBAYASHI, Paul H. SHINGU

1988 Volume 38 Issue 4 Pages 222-227
Published: April 30, 1988
Released on J-STAGE: July 23, 2008

DOIhttps://doi.org/10.2464/jilm.38.222

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Rapidly solidified Al-Si ribbons prepared by the single roller method were pulverized by the use of vibration mill. The milled powders were consolidated at different temperatures by the strained powder rolling method. P/M alloys have a density more than 95% of that of metal mold cast alloys. Hypereutectic P/M alloys have uniform distribution of fine Si particles in the structure. When rolled at 573K, the Siparticles are 1 to 5μm in diameter. P/M alloys harden with increasing Si content and soften at higher rolling temperatures. Tensile strength and elongation of P/M alloys are higher than those of metal mold cast alloys containing Si 20at% or more. 30at% Si P/M alloy has tensile strength about 33kg/mm² and elongation about 5%.

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Plasticity of Al₃Ti and possibility of its being improved

Masaharu YAMAGUCHI, Fujinobu NAKAMURA, Yasuharu SHIRAI

1988 Volume 38 Issue 4 Pages 228-237
Published: April 30, 1988
Released on J-STAGE: July 23, 2008

DOIhttps://doi.org/10.2464/jilm.38.228

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High purity aluminum

Harumi KOSUGE

1988 Volume 38 Issue 4 Pages 238-248
Published: April 30, 1988
Released on J-STAGE: July 23, 2008

DOIhttps://doi.org/10.2464/jilm.38.238

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Thinkings of Writing

Masami MATSUDA

1988 Volume 38 Issue 4 Pages 249-250
Published: April 30, 1988
Released on J-STAGE: July 23, 2008

DOIhttps://doi.org/10.2464/jilm.38.249

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Erratum to : Effect of solidification conditions on mechanical properties of unidirectionally solidified EZ33A alloy

1988 Volume 38 Issue 4 Pages iva
Published: 1988
Released on J-STAGE: July 23, 2008

DOIhttps://doi.org/10.2464/jilm.38.4_iva

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