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Volume 27, Issue 5
Displaying 1-6 of 6 articles from this issue
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Shiro SATO, Noboru OKOSHI1977 Volume 27 Issue 5 Pages 211-216
Published: May 30, 1977
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDifferent sizes of tensile test specimens were extracted from three kinds of butt-welded plates in thickness 6, 12 and 22mm. Tensile strength of welded joints rises to a definite value as the ratio of W/t increases (W: specimen width, t: specimen thickness). 0.2% proof stress obtained on 50mm gage length with the weld in the center is free from the effects of W/t. But, if the weld metal is remarkably lower in strength than the base metal, the proof stress slightly decreases with increase in W/t. Barba's law representing a relation between elongation and size of specimen is applicable to the welded joint in which a slight difference lies between strengthes of the base metal and weld metal. For the welded joints having weld metal of lower strength, Barba's law is applicable only to the specimens having large values of W/t. The ductility of welded joints can be expressed by the elongation against L0 = 5.65√A in the similar way to the ordinary tensile test (L0: gage length, A: cross sectional area).View full abstractDownload PDF (616K) -
Yutaka NAKAYAMA, Taichiro ITO, Shinya TAKENO1977 Volume 27 Issue 5 Pages 217-223
Published: May 30, 1977
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSWhen aluminum single crystals prestressed in tension at room temperature were deformed in tension at temperatures 100° to 300°C, the recovery of deformed structure resulted in yielding phenomena. The prestress so large to ensure the formation of cell structure is required to present the yielding phenomena at elevated temperatures. The yield drop Δτ increases as the prestress increases. The critical resolved shear stress in the specimens held at elevated temperatures for the same time decreases as the temperature rises in contrary to Δτ. If the yielding phenomena are presented, slip lines are coarsened, curved, diffused and localized. As the holding time is prolonged, CRSS and Δτ decrease. The specimens prestressed by 750g/mm2 and held at 200°C for 60min or at 300°C for 30min are free from yielding phenomena. Dislocations introduced at room temperature rearrange to long straight on one's way to form stable subboundaries during holding at elevated temperatures. Significant yielding phenomena are presented when deformed in this condition. The stress necessary to bow out the straight dislocations remarkably contributes to CRSS. The characteristic slip lines described above are formed when the slip initiates in a subgrain and preferentially propagates to the neighboring subgrains. After the stable subboundary is completed, the deformation is restricted in it and no more the yielding phenomena appear.View full abstractDownload PDF (2925K) -
Tadakazu OHNISHI, Yoshizo NAKATANI1977 Volume 27 Issue 5 Pages 224-231
Published: May 30, 1977
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSStress corrosion cracking tests were carried out in 3.5% NaCl solution. In a normal stress corrosion test, hydrogen bubbles generated at grain boundaries after some period from a start of testing and cracks were visualized. Cracks propagated along the grain boundary with increasing the number and size of bubbles. As a corrosion reaction was activated by anodic current in an accelerated test, hydrogen bubbles generated earlier and larger, and generated also at grain boundaries where no crack nucleated and in the grains. The crack propagated at an average rate 0.1-3mm/hr, but the propagation was microscopically discontinuous and the maximum rate reached 10-50mm/hr. Dissolution models for the stress corrosion mechanism is unapplicable at least for Al-Mg alloys. The stress corrosion involves both corrosion and mechanical processes.View full abstractDownload PDF (3653K) -
Motohiro KANNO, Hisashi SUZUKI, Mikio FUJII1977 Volume 27 Issue 5 Pages 232-238
Published: May 30, 1977
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe initial rate of aging in Al-Cu base alloys has been experimentally derived assuming that experimental aging curves are expressed by an empirical formula, Δρ/ρ0=(1/b)ln{(a+btA)/a}, where Δρ is resistivity change, ρ0 as-quenched resistivity, tA aging time, and a and b constants. This paper describes whether the above assumption is really adequate or not. The time required for up-quenching the specimen from -196°C to aging temperatures 0 to 40°C was unexpectedly prolonged because of the sharp decrease in up-quenching rate near the aging temperatures. This suggested that the aging curves generally drawn by repeated aging method were not so accurate particularly in their initial parts. On the other hand, even in the continuous aging method susceptible to a little influenc of up-quenching, the initial rate of aging could not be accurately obtained by use of the formular. When the aging curves artificially constructed so as to correspond to the above formula were examined, calucalated values of (dt/dρ) seemed to be approximated by (Δt/Δρ). But such approximation resulted in a considerable error in the value of a, especially in the aging curves having high initial rate. The accurate initial rate of aging appeared to be obtained in neither repeated nor continuous aging method so far as the above equation was applied for analysis of aging curves.View full abstractDownload PDF (877K) -
Hisashi SUZUKI, Ichiro ARAKI, Motohiro KANNO, Kazuhiro ITOI1977 Volume 27 Issue 5 Pages 239-245
Published: May 30, 1977
Released on J-STAGE: November 05, 2008
JOURNAL FREE ACCESSThe aging behaviors of Al-2%Cu-0.9%Mg alloy have been studied paying attention to the effect of Si addition up to 0.5% by means of hardness, calorimetric and electric resistivity measurements and transmission electron microscopy. Specimens were solution-treated at 505°C, water-quenched and subsequently aged mainly at 200°C.
The hardness of aged ternary alloy was remarkably increased by adding Si, probably due to the change in aged structures that there appeared three sorts of precipitates in Si added alloys in contrast to one sort of precipitate (S') in the ternary alloy. Si addition was effective only when the specimen was water-quenched and not direct-quenched in an aging bath. On the other hand, the Si addition to ternary alloy having higher solute contents, that is, Al-4%Cu-1.8%Mg alloy was found to have a tendency to lower the hardness after aging.View full abstractDownload PDF (3500K) -
Umewo HONMA, Junichi SATO, Akihiko KAMIO1977 Volume 27 Issue 5 Pages 246-260
Published: May 30, 1977
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (2595K)
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