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Volume 22, Issue 3
Displaying 1-8 of 8 articles from this issue
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Kojiro KOBAYASHI, Paul Hideo SHINGU, Ryohei OZAKI1972 Volume 22 Issue 3 Pages 165-174
Published: March 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe nature and origin of so called "over modification band" which appears in the microscopic structure of eutectic Al-Si alloy treated with an excessive amount of sodium has been investigated in detail by the method of 1) the optical and scanning electron microscope observation of structures, 2) the X-ray microprobe analysis of the distribution of sodium in solidified structures and 3) the change in the thermal analysis curves depending on the added amount of sodium.
The over modification band may be classified into two groupes. The first group of band is formed when the temperature gradient in the liquid in front of the solid-liquid interface is decreased abruptly, for example, when the melt is cast in an insulating mold. The increase in sodium concentration and the decrease in temperature gradient results in the increase in the constitutional supercooling of aluminum. The condition will be satisfied for the change from the co-operative Al-Si eutectic growth with a plane solid-liquid interface to the dendritic growth of aluminum. The dendrite of silicon is not formed due to the existence of excess amount of sodium. When the growth of aluminum dendrite reaches to certain extent, the supercooling will be reduced and the co-operative growth of the eutectic is resumed leaving behind the "band" of aluminum dendrites with coarse silicon particles in between.
The second group of band is formed due to the local segregation of sodium when the sodium addition is highly excessive. The band formed in such case is composed of aluminum dendrites, silicon particles and a ternaly compound having chemical composition close to AlSiNa.
The formation of over modification band, in the case of either groupes, is governed by the solidification rate, temperature gradient at the solidliquid interface and the sodium content of the liquid. Therefore, by the proper consideration of the solidification condition, the formation of the band may be avoided even when the sodium content is in excess.View full abstractDownload PDF (3807K) -
Studies on stress corrosion cracking of Al-Zn-Mg alloys (5th report)Toshio SAITO, Takakazu TANAKA1972 Volume 22 Issue 3 Pages 175-181
Published: March 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSTear tests, tensile tests, and stress corrosion tests of Al-Zn-Mg alloys were conducted to examine the relationship between tear resistance and stress corrosion cracking.
The results obtained were as follows:
(1) There was no complete correspondence between the sensitivity to stress corrosion cracking and unit propagation energy (UPE), But on the specimens heat-treated under the same or similar condition, there was much correspondence between them. It would probably be due to the smooth crack propagation that an Al-Zn-Mg alloy age-hardened for high strength is more brittle and more sensitive to stress corrosion cracking.
(2) The form of grain boundary in the loading direction would have great effects on the directional dependence of mechanical and stress corrosion properties. The directional dependence did not appear in specimens having equi-axial grains. Whereas, the directional dependence clearly appeared in stress corrosion tests, because the crack always propagated along the grain boundary.View full abstractDownload PDF (1077K) -
Studies on aluminum surface and its adhesive strength (1st report)Takashi ABE, Toshimitsu UCHIYAMA, Eizo ISOYAMA, Takao MURAKAWA1972 Volume 22 Issue 3 Pages 182-192
Published: March 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSEffects of the surface films of aluminum on adhesion of polyethylene were investigated by the relationship between peeling strength and thickness of the oxide films or by observation of the surfaces under a scanning electron microscope.
The following conclusions were drawn from the experiments:
(1) The increase in thickness of the films greatly depended upon the heating temperature, and the adhesive strength decreased with the increase of the thickness. In other words, adhesive failure between aluminum surface and polyethylene or cohesion failure in the polyethylene film occurred on electro-polished aluminum specimens; while, cohesion failure in the oxide film was observed on aluminum oxidized in the air at high temperatures.
(2) Adhesive strengths of anodic oxide films and some converted films such as boehmite film and chromate film were greater than those formed in the air.
Therefore, cohesion failure in the polyethylene film was observed in these aluminum specimens.View full abstractDownload PDF (2661K) -
Kizo SHIBATA, Hiromitsu KAMON, Shoichi ANADA, Kiyoshi TAKESHITA1972 Volume 22 Issue 3 Pages 193-198
Published: March 30, 1972
Released on J-STAGE: November 05, 2008
JOURNAL FREE ACCESSThe sealing mechanism was studied on the pore structure of thin oxide coatings of aluminum which had been anodized in sulfuric or chromic acid bath. The sealing was made in boiling water or in a steam autoclave. The coatings were heated in vacuum at various temperatures of 20∼400°C, and the pore structure was examined by nitrogen adsorption isotherms at -196°C.
The following results were obtained:
(1) The pores of anodic oxide coatings were filled by sealing almost perfectly; but the pores of chromic acid coating were not sealed in boiling water at 100°C for 30min.
(2) The sealed anodic oxide coatings were dehydrated by vacuum heating at temperatures higher than 150°C and a large number of pores were formed on their surfaces. The pore size distribution curves of the coatings were different according to the methods of anodizing and sealing.View full abstractDownload PDF (644K) -
Shinichiro FUJIKAWA, Kenichi HIRANO1972 Volume 22 Issue 3 Pages 199-210
Published: March 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe effects of gold addition (0.00070.04at.%) on the age-hardening of Al-5wt.% (2.09at.%) Zn-2wt.% (2.24at.%) Mg alloy were investigated by measurements of hardness, tensile tests, and electron microscopy.
The following results were obtained:
(1) Addition of a small amount of gold remarkably accelerated the age-hardening of Al-Zn-Mg alloy during the ageing in the temperature range of from room temperature to 150°C, particularly at 120°C.
(2) It was shown by electron microscopy that the addition of gold increased the number of precipitated particles which were more uniformly distributed, and made the width of no-precipitate zone along grain boundaries smaller as compared with the case in the pure ternary alloy.
(3) The acceleration of age-hardening by the gold addition may be attributed to the increase of G. P. zones and η'-phases nucleated. Accelerated nucleation of G. P. zones and η'-phases in the alloy containing gold would be related with the fact that the addition of gold reduces the interfacial energy of the critical nucleus of G. P. zones and also acts as catalytic potential for the nucleation of η'-Phases.
(4) The addition of gold was found to have an effect to improve the ductility (elongation) of the alloy in the age-hardened state as well as the effect to accelerate the hardening. These effects depended upon ageing temperature, ageing time, and the additional amount of gold.View full abstractDownload PDF (2187K) -
Texture of rolled sheets of growth twinned aluminum (1st report)Nobukatsu BEKKU, Umewo HONMA, Shigeo OYA1972 Volume 22 Issue 3 Pages 211-220
Published: March 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe crystallographic orientation of polycrystalline cast aluminum can be three-dimensionally controlled only by "regrowing" lamellar growth twin crystals from seed crystals. In this work, the aluminum cast blocks having six different orientations produced by this technique were rolled in order to determine the dependence of the rolling textures on the initial orientations.
The rolling textures of aluminum mainly depends upon the initial orientations. The transitions of initial orientations to the rolling textures during rolling are:
orientation texture
{110}<112> and{112}<110> →{110}<112>
{112}<111> →{112}<111>
{110}<111> →n{225}<353> or{112}<111>
{111}<112> →{157}<533>+{110}<225>
{111}<110> →{110}<335>+{135}<225>
{hkl}<100>columnar crystals →{110}<114>+{110}<001>
Equi-axed random crystals →n{146}<211>+{112}<111>
The orientations {110} <112> and {112} <111> are found to be stable in the rolling textures on the basis of experiments and analyses of slip systems. The orientation n {146} <121>, representing an intermediate orientation between {110} <112> and {112} <111>, is also found stable by experiments, but its little substantial evidence is given by analyses of slip systems.View full abstractDownload PDF (1008K) -
Textures of rolled sheets of growth twinned aluminum (2nd report)Nobukatsu BEKKU, Umewo HONMA, Shigeo OYA1972 Volume 22 Issue 3 Pages 221-228
Published: March 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe orientation of polycrystalline aluminum can be three-dimensionally controlled by "regrowing" lamellar growth twin crystals 2). It was demonstrated in the preceding papery 1) that the rolled textures depend upon the initial orientations by using aluminum cast blocks which have been three-dimensionally orientated in such a way. The recrystallization textures of aluminum sheets were determined, in this work, study, in order to accomplish the transitions from rolled to recrystallized and from initial to recrystallized textures.
The transformation of rolled to recrystallized textures are:
Rolled texture recrystallized texture
{110} <112> →{110} <112> +ω{110} <001> at 350°C
"→{110} <001> +{123} <331> at 500°C
{112} <111> →{001} <410> +n{123} <334>
n{225} <335> →{112} <123> +{100} <001>
{157} <335> →{135} <112> +ω{110} <001> +n{133} <321>
n{113} <553> +{110} <225> →n{113} <553> +{110} <225> at 350°C
"→n{113} <335> {110} <115> at 500°C
Three types of dependence of recrystallized textures on rolled ones are found:
(1) Both of the textures are the same or similar.
(2) The both have a conjugate <111> axis of rotation.
(3) The both are independent.
The recrystallized textures incidentally depend upon the initial textures. Each of the oriented growth and oriented nucleation, theories is incomplete for the explanation of recrystallizing behavior. The nucleating and growing stages for recrystallization would be noteworthy.View full abstractDownload PDF (867K) -
Haruo KOBAYASHI1972 Volume 22 Issue 3 Pages 229-248
Published: March 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (2024K)
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