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Volume 22, Issue 2
Displaying 1-8 of 8 articles from this issue
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Takuro SAGA, Kinji SATO1972 Volume 22 Issue 2 Pages 91-100
Published: February 28, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSFor the precise working in folding operation of aluminum sheets, it is necessary to examine the bending process in more detail.
The following problems are discussed in this paper for this purpose.
(1) Variation of strain with the progress of bending process.
(2) Change in aspect of bending process with the change in clearance.
(3) Comparison between theoretical and experimental values of vertical punching force.
As the results of experiments, it was found that the magnitude and distribution of strain and the displacement of the neutral plane from the middle of sheet thickness largely depended upon the radius of die. The spring back was larger and a better agreement was shown between calculated and experimental values of vertical punching force with the increase in the value of clearance.View full abstractDownload PDF (1001K) -
Yuji MATSUURA, Mitsugu MOTOMURA, Toshio TANAKA1972 Volume 22 Issue 2 Pages 101-112
Published: February 28, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSCompression tests of a block between parallel plates are usually applied to determine the stress-strain curves in compression under plane-strain condition such as in rolling, and to estimate the "reduction capacity" of lubricants.
It is clear that these tests are based on the compression under plane-strain condition. However, it will be necessary to confirm whether the compressive deformation of a block between parallel plates occurs under the plane-strain condition.
The pressure distribution in the contact area between the material and the parallel plates was studied by the method of "pressure pick-up pin" under various conditions of different thicknesses of specimens, lubricants, reduction percentages, and thickness ratios (b/t0).
The results obtained were summarized as follows:
(1) When the thickness ratio (b/t0) was a positive integer, the value of specific yielding point stress (po/2k) was approximate to 1.
(2) The pattern of contact pressure distribution in the direction of die width did not much depend upon lubricant conditions, thickness ratio, and reduction percentage. However, high pressure appeared in the middle part and near the ends of the die width, and lower pressure appeared in the intermediate parts.
(3) As for the contact pressure distribution in the direction of larger length of die, the pressure showed maximum in its center and gradually decreased toward ends (plotting a convex curve) under good lubrication. Whereas, in bad lubrication, the maximum pressure appeared at several mm apart from the center, which plotted a concave curve.
(4) When a block, having the same width as the die, was compressed between parallel plates, the pressure distribution along the larger length of die was nearly constant, which was called "flat pattern".
(5) The leading factor affecting the pressure distributions in the compression of a block between parallel plates was the non-contact deformed part on both sides of the contact part between the die and specimen. The above part constrained the flow of material in the directions of width and length, and produced various patterns of pressure distribution.View full abstractDownload PDF (1506K) -
Takuichi MORINAGA, Tsuneo TAKAHASHI, Yo KOJIMA1972 Volume 22 Issue 2 Pages 113-119
Published: February 28, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSStudies were made of the effects of Mn content (0.2, 0.4 and 0.6%) on mechanical properties, the resistance to corrosion fatigue, and the resistance to stress corrosion cracking of Al-Mg casting alloys.
The results obtained were summarized as follows:
(1) The strength of Al-Mg alloys increased, but the elongation decreased with increasing Mg and Mn contents.
(2) The corrosion resistance of Al-3.56.5%Mg casting alloys was very high. In particular, their susceptibility to stress corrosion cracking was much lower than that of Al-10%Mg casting alloys.
(3) The corrosion resistance of Al-3.5%Mg alloys increased, but that of Al-6.5%Mg alloys decreased with increasing Mn content.View full abstractDownload PDF (1337K) -
Mamoru IMABAYASHI1972 Volume 22 Issue 2 Pages 120-127
Published: February 28, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSIt was explained in the previous paper that stationary concentration of hydrogen in molten aluminum depended upon the melting processes.
This paper discusses the effects of humidity in the atmosphere on hydrogen concentration in molten aluminum. Supplementary experiments were also performed to study the effects of melting process on stationary concentration of hydrogen in the melt.
Molten aluminum (99.99% in purity) was held in the atmosphere, of which the humidity was controlled by six stages, and their hydrogen contents were measured at intervals of a certain time. The results showed that the stationary concentration of hydrogen (Cs) could be expressed by function of the humidity (P<H2O>) as follows:
Cs = K√P<H2O>
As the results of the supplementary experimants and the above relation between Cs and P<H2O>, the following considerations were drawn concerning the effects of melting process on Cs.
(1) It was due to the higher humidity in the atmosphere that Cs of the melt held in a resistance furnace sealed with a cover was higher than that held in an induction furnace.
(2) It was due to the disposition of interface between the melt and crucible that hydrogen in aluminum, which had been melted in vacuo, increased with the holding time in the air, but not converged into a stationary concentration.View full abstractDownload PDF (1229K) -
Hajime YAMADA, Motoyoshi ITO1972 Volume 22 Issue 2 Pages 128-134
Published: February 28, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThese studies were made to investigate the effects of Si on the recrystallization of Al-Mn alloy.
(1) Si had remarkable effects on the recrystallization temperature of Al-Mn alloy. When its sheet ingot was not preheated, Si raised the recrystallization temperature. Whereas, when it was preheated. Si lowered the temperature.
(2) Heating rate also had effects on the recrystallization temperature of non-preheated Al-Mn alloy containing Si. The elevation of temperature was remarkable in slow heating, and it was maximum at the heating at 160°C.
(3) Si decreased the effects of heating rate on the grain size of recrystallized Al-Mn alloy when the sheet ingot was not preheated. It gave a fine grain size even at slow heating rate. Whereas, Si increased the effects of heating rate on the grain size of the preheated alloy and a large grain size was produced by slow heating.
These phenomena resulted in that Si prevented the effects of preheating on the refining of the recrystallized grains of Al-Mn alloy; and the grains obtained at the normal heating rate, which was slower than that in a salt bath, were coarser than those obtained after no preheating.View full abstractDownload PDF (2010K) -
Hisashi SUZUKI, Shigenori ASAMI, Motohiro KANNO1972 Volume 22 Issue 2 Pages 135-142
Published: February 28, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSEffects of the composition on the ageing processes of (α+T) two-phase Al-Zn-Mg alloys were investigated by electric resistivity measurement, hardness measurement, and transmission electron microscopy mainly in the temperature range of 80150°C. Specimens were solution-treated at 470°C, quenched, and finally subjected to isochronal and isothermal ageing.
The results were summarized as follows:
For example, even the total amount of (Zn+Mg) was a definite value in at%, the ageing processes of the alloy system were confirmed to vary in the following way with the increase in Zn/Mg ratios in the specimen.
The rate of increase in resistivity and the maximum value of resistivity obtained became higher when TA<T<G. P.> (where TA: ageing temperature and T<G. P.>: temperature of solubility limit in G. P. zone of each specimen). But, the rate of decrease became higher when TA<T<G. P.>
On the other hand, the rate of hardening and the maximum value of hardness obtained became higher at any of TA. However, there was a tendency to overageing due to η phase precipitation. The distribution of η' phase in grains was finer in the state of the maximum hardness of specimens. The width of PFZ, which was considered to be due to the grain boundary precipitation, became smaller.
It was suggested that Zn-vacancy pairs and free vacancies played an important role in the ageing processes even in such a high temperature ageing as being expected from the results of low temperature ageing or calorimetric studies previously reported.View full abstractDownload PDF (2405K) -
Studies on growth twin crystals in aluminum and aluminum-base alloys (3rd report)Shintaro MIYAZAWA, Umewo HONMA, Shigeo OYA1972 Volume 22 Issue 2 Pages 143-150
Published: February 28, 1972
Released on J-STAGE: November 05, 2008
JOURNAL FREE ACCESSA procedure has been established in the preceding work to permit substantial generation of growth twin crystals in aluminum on the basis of the nucleation theory developed and demonstrated by the present authors. This paper describes characteristic growth behaviors of growth twin crystals of pure aluminum and an Al-Mg alloy. The temperature gradient G in the liquid just ahead of the advancing interface, growth rate R and other solidification variables were determined on the growth twin crystals unidirectionally "regrowing" from seed crystals.
Both columnar and growth twin crystals of pure aluminum competitively grow in the early stage of unidirectional solidification at a cooling rate approximately 20°C/min or more, G more than 10°C/cm, and R more than 2.0cm/min. If G and R are decreased with lowered cooling rate, the growth twin crystals gradually advance ahead of the columnar crystals. Growth twin and columnar crystals of the Al-10at.%Mg alloy, on the other hand, competitively grow at a cooling rate approximately 70°C/min or more, G more than 30°C/cm and R more than 2.2cm/min. The growth twin crystals gradually proceed at less G and R. Decrease in R with advancing the freezing front is tangential in unidirectional growth of twined crystals, but is quadric in that of columnar crystals. The twining growth allows wider ranges of R and G/R than the columnar growth. The G/R ratio depends on the topography of the interface characteristic in each type of crystals. Growth twin crystals have interfacial topographies closer to planar than those of columnar crystals even during the competitive growth.
The twin plane lies across the center of a cell. The width of a growth twin crystal or a twin spacing is proportional to a squre root of growth rate.View full abstractDownload PDF (1900K) -
Ichiro KAWAKATSU1972 Volume 22 Issue 2 Pages 151-163
Published: February 28, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (2515K)
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