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Volume 21, Issue 5
Displaying 1-6 of 6 articles from this issue
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Mototaro SATO, Yoshio KATO1971 Volume 21 Issue 5 Pages 315-323
Published: May 30, 1971
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe object of these studies is to examine the change in cutting conditions with the progress of drilling for determining the optimum conditions in the experiments of drilling deep holes in aluminum cast alloy AC8B.
The results obtained were as follows:
(1) The torque was linearly increased with the increase of hole depth. However, the thrust was nearly kept constant owing to the difficulty in removal of chips, except for temporary variations.
2) The cutting resistances of heat-treated (T5 and T6) specimens were higher than that of as cast (F) specimen. In particular, the resistance of T6 was the highest among them. These results would be due to the fact that there is a relationship between cutting resistance and tensile strength or hardness of the material.
3) The depth of holes per one step feed greatly depended upon the feeding speed and the twisting angle of the drill. According to the data in these experiments, the effective twisting angle and feeding speed of the drill in drilling of deep holes were about 30° and 0.05 mm/rev., respectively.View full abstractDownload PDF (1919K) -
Studies on heat treatments of aluminum alloy castings (1st report)Kimio KIMURA, Masataka MURAKI, Takao HAYAKAWA1971 Volume 21 Issue 5 Pages 324-336
Published: May 30, 1971
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSHeat treatment (T5 treatment) for improving dimensional stabilities was conducted on five sorts of typical aluminum casting alloys; AC2B, AC4B, AC4C, AC5A, and AC8B,
Casting stress, growth produced by heating to a high temperature, and mechanical properties were measured on the specimens, which had been heat treated under various T5 conditions, and optimum conditions of T5 treatment were determined
The principal results obtained were as follows:
1) Aluminum alloys containing appreciable amounts of slicon such as AC2B, AC4B, AC4C, and AC8B exhibited growths of 0.00100.0013mm/mm at maximum when heated to 250°C.
However, such a growth was not exhibited by an alloy containing less silicon such as AC5A.
For preventing such growths of aluminum alloys containing silicon, it was recommended to perform T5 treatment at 200°C for 10hrs., at 230°C for 3hrs., or at 250°C for 1hr.
(2) The casting stesss was increased with the increase in copper content in aluminum alloys.
AC5A exhibited the largest casting stress. It was diffcult to relieve its stress by conventional T5 treatments, but the stress was substantially relieved by further T2 treatment at 350°C for 3hrs.
Whereas, AC4C exhibited the smallest casting stress. Any T5 treatment was not needed to relieve its stress, or if necessary, the ageing at 250°C for 3hrs. would be enough.
3) Some of the methods of heat treatment specified in JIS, MIL, SAE, CSA, etc. are not effective in stress relieving or in preventing growth of castings.
You must be careful in application of these specifications to effective heat treatments of aluminum alloy castings.View full abstractDownload PDF (1553K) -
Studies on heat treatments of aluminum alloy castings (2nd report)Kimio KIMURA, Masataka MURAKI, Takao HAYAKAWA1971 Volume 21 Issue 5 Pages 337-349
Published: May 30, 1971
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSA study on T5 treatment for improving dimensional stabilities of aluminum alloy castings as cast was described in the 1st report.
This paper describes T7 and other heat treatments for improving dimensional stabilities for five sorts of typical aluminum alloy castings as quenched; AC2B, AC4B, AC4C, AC5A and AC8B.
The optimum conditions of heat treatments were determined by test results of quenching stress, growth produced by heating to a high temperature, and mechanical properties.
The principal results obtained were as follows:
1) Aluminum alloys as quenched, containing appreciable amounts of silicon such as AC2B, AC4B, AC4C, and AC8B exhibited growths of 0.00090.0012mm/mm at maximum when heated to 250°C.
However, such a growth was not exhibited by an alloy containing less silicon such as AC5A.
These results of the alloys as quenched were almost the same as those of as cast in the 1st report.
2) It was effective to perform T7 treatment at 200°C for 15hrs., 230°C for 8hrs., or 250°C for 3hrs. for preventing such growths of aluminum alloys containing silicon.
3) AC5A and AC8B exhibited the largest quenching stress and AC4C exhibited the smallest.
When the alloys liable to exhibit large quenching stresses were subjected to T7 treatment or a short time annealing after T6 treatment, the quenching stresses were not perfectly relieved and mechanical properties were markedly reduced.
T6 treatment involving oil or air quenching was effective in obtaining the optimum conditions of the alloys with high strength and small residual stress.View full abstractDownload PDF (1534K) -
Studies on solidified structure and properties of Al-Si-Cu alloys die castings (3rd report)Muneo SUZUKI, Kazuyuki FURUMOTO1971 Volume 21 Issue 5 Pages 350-357
Published: May 30, 1971
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThis paper describes the correlation between the quantitative measurements of cast structure and mechanical strength of Al-12 Si-Cu alloy (JIS ADC 12) die castings.
The results obtained were summarized as follows:
1) Dendrite cell size was found to be more than 1/10 times smaller than that of sand castings. The size was linearly smaller from the surface toward the center of the castings.
Eutectic silicon was in spherical form of about 1 μ in diameter at 0.050.1mm from the surface. However, it gradually turned to acicular and larger in size toward the center. The value of axis-ratio was varied in the range of 3.413.8.
The ratio of crystallized α phase area was rapidly increased with the depth of up to 0.5mm from the surface, and then, it was kept nearly constant toward the center.
2) Correlation was observed between measurements of cast structure and mechanical strength. It was found that the immediate cause of strength lowering was attributed to the coarsening of cell size and grain growth of eutectic silicon.View full abstractDownload PDF (2336K) -
Sei MIURA, Hideo KAWANO1971 Volume 21 Issue 5 Pages 358-365
Published: May 30, 1971
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe relation between strain aging and Portevin-LeChatelier effect (dynamic strain aging) was studied for clarifying the mechanism of P-L effect.
Experiments for strain aging were conducted on Al-1at.%Mg alloy which had been stretched by 2%at-60°-20°C, and then, aged at the deformation temperature under interrupted load.
The strain aging process was divided into two stages. The 1st stage of less than 7sec. in aging time approximately conformed to the time law of t2/3 and the activation energy was found to be 0.21eV. The time law in the 2nd stage, more than 10sec. in aging time, was approximately to t1/3 and the value of activation energy was 0.45eV. The activation energy in the 2nd stage was interpreted as the migration energy of pairs of Mg atom-single vacancy. The activation energy of 0.60eV previcusly found in the process of P-L effect of this alloy was assumed to be the migration energy of Mg atom-single vacancy pairs, part of which move by cutting the binding between the Mg atom and the vacancy, becuase P-L effect occurred at higher temperature than that for strain aging.
It was noted that the vacancies induced by strain played an important role in appearance of yield point due to strain aging form the results of experiments for eliminating the vacancies which had existed before the occurrence of strain aging. As the results of above studies, it may be concluded that P-L effect is the phenomenon in which strain aging occurs during plastic deformation.View full abstractDownload PDF (883K) -
Yotaro MURAKAMI1971 Volume 21 Issue 5 Pages 366-377
Published: May 30, 1971
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (1729K)
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