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Volume 20, Issue 7
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Studies on the stress corrosion cracking of Al-Zn-Mg alloy (4th report)Takakazu TANAKA, Toshio SAITO1970 Volume 20 Issue 7 Pages 321-330
Published: July 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThese studies were made to examine the effects of two-stepped aging on the stress corrosion cracking of Al-Zn-Mg alloys.
Al-6Zn-3Mg alloy was aged in two steps under several conditions. The stress corrosion cracking test were performed on the above two-stepped aged alloys to pursure factors affecting the stress corrosion cracking.
The results obtained were summarized as follows:
(1) The stress corrosion cracking tests were performed on the alloy which had the maximum strength on the final aging curve. The stress applied was 75% of the proof stress of the specimens. The resistance to the stress corrosion cracking was lower when the preaging temperature was higher and its time was longer.
(2) In the alloy which was sensitive to the stress corrosion cracking on the above tests, the size of the precipitated particles was fine and the change in surface roughness due to the tensile deformation was great.
The sensitivity to the stress corrosion cracking did not depend only on the width of precipitate free zone on the grain boundary, but also on other factors.
(3) It has been thought that the two-stepped aging reduces the sensitivity to the stress corrosion cracking of Al-Zn-Mg allys. It may be due to the following two reasons.
In general, the stepped-aged alloy has higher strength than the alloy ordinally aged. Then, the former specimen will have higher resistance to deformation and also to stress corrosion cracking than the latter when the both specimens were subjected to the stress corrosion cracking tests under the load of the same weight.
The other reason would be due to the difference in aging stage. When the final aging of the both specimens was performed under the same conditions, the former specimen will be more advanced in aging than the latter. The sensitivity to stress corrosion test is generally low in over-aged alloys. Then, the former specimen, which is more advanced in aging, will have higher resistance to stress corrosion cracking than the latter.
(4) The electrode potential and the weight loss by normal corrosions were not closely related with the stress corrosion cracking. As well known, pitting corrosions often occurred on the specimens sensitive to the stress corrosion cracking.View full abstractDownload PDF (1969K) -
Tsuyoshi HIRAMATSU, Yoshimitsu MIYAGI, Kiyoshi NAGAO, Makoto SHIMADA1970 Volume 20 Issue 7 Pages 331-335
Published: July 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe stress corrosion cracking of metals is caused by the simultaneous attack of special chemical reactants and tensile stress. Accordingly, it is affected by several factors in environments.
In this paper, these are investigated on the effects of outdoor atmospheric environments on shear cracks of a commercial Al-Zn-Mg alloy. The cracks mean the stress corrosion cracking in the short transverse direction due to the residual stress caused by shearing.
The occurrence of the shear cracks was varied according to the season of the year. They were not likely to occur during the period from October to April, but were liable to occur from May to September; especially from July to August. Therefore, it was recommended for the stress corrosion cracking tests in the outdoor atmospheric environments that the exposure would be started in April to select the test peiod of at least 6 months from April to September. The specimens, which were not cracked during the above period, were supposed to be not cracked during the following 6 months from October to March.
The effects of several factors in outdoor environments on the shear cracks were also discussed. It was suggested that Cl- was an important factor as well as temperature and humidity affecting the cracks.View full abstractDownload PDF (641K) -
Shigeo ZAIMA, Kanji TAKIMIZU1970 Volume 20 Issue 7 Pages 336-341
Published: July 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThis paper describes the texture of the surface layer of commercial pure aluminum plate, (1100) which was formed by orthogonal cutting by low speed two-dimensional machining. Especially, the structure was discussed for the pole figure obtained by X-ray diffraction method in order to study the cutting mechanism of aluminum. The results obtained were summarized as follows.
It was found by X-ray diffraction that the cut surface layer represented a sort of fibrous structure. In the texture before cutting, the orientation (100) [011] was co-exist with (111) [112]; but after cutting, the orientation (111) [112] decreased and (100) [011] was predominant, which showed that the outer surface consisted of a texture which slightly leaned from (100) [011] orientation to the cutting direction. The above tendency was more distinct with the increase in the depth of cut. Even a cast aluminum plate of the same composition as 1100, which represented not so evident texture before cutting, also showed a texture similar to that of the previous specimen after cutting.
The authors discussed the fact that the above structures were nearly dentical with the structure of surface layer of cold rolled plates and suggested that the fibrous structure can be detected by etching pit method.View full abstractDownload PDF (1274K) -
Studies on Al-Zn-Mg, T6 alloyShiro SATO1970 Volume 20 Issue 7 Pages 342-348
Published: July 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe specimens used for these tests were plates of Al-Zn-Mg, T6 alloys in thicknesses of 5 and 10 mm. The test results obtained were compared with those of 5052-O alloy in the previous works.
The 1st tests were to investigate the effects of change in width of reduced section on tensile properties of the material, maintaining the length of the section constant.
The 2nd tests were to investigate the effects of change in length of reduced section on tensile properties of the material, having two different widths.
The principal results obtained were as follows.
(1) The size and shape of the test specimens had substantially no effects on proof stress or tensile strength of the material measured.
(2) The elongation measured in a constant gauge length increased with the increase in value of W/T or Lc/W (in which W, T and Lc are width, thickness and length of the reduced section, respectively).
(3) The region of shoulder which constrained the strain distribution near the end of the reduced specimen was about 0.3 W in length from the end of the straight section. This value was nearly equal to that previously obtained in 5052-O alloy.
(4) A relation between δ and L0√A (in which δ: elongation percentage, L0: gauge length, and A: cross-sectional area of specimens) was obtained from the experimental results. It was also found that δ for the same value of L0√A decreased with the decrease in Lc/W. The latter relation was different from that previously obtained in 5052-O alloy.
(5) The length of the reduced section of sheet metal specimens of Al-Zn-Mg T6 material would preferably be in the range of Lc/W≥6 for these tension tests.
(6) The elongation equation for 5052-O alloy fairly conformed to Barba's Law of Similarity. However, there was no uniform elongation outside the neck in Al-Zn-Mg T6 alloys. Accordingly, judging from the figures of strain distribution curves, Oliver's Elongation Formula would be applicable to the latter alloys.View full abstractDownload PDF (752K) -
Syotaro MIZOBUCHI, Toshio NAKAMURA, Nobumitsu KITASHIMA1970 Volume 20 Issue 7 Pages 349-356
Published: July 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSIn recent days, Al-Zn-Mg alloys have been attracting public attention as high strength aluminum cast alloys, though they are poor in ductility. The residual stress of these alloys due to casting and heat treatment lowers fatigue limit and facilitates stress corrosion cracking and brittle rupture. Therefore, there are many problems to be discussed in their practical uses. In this study, residual strain was mechanically measured by using strain gauges and the distribution of internal stress was calculated by Sachs' Equation. Surface stress was measured by X-ray and Bühler's mechanical methods.
The results obtained were as follows:
(1) The residual stress due to casting was less than 0.8 kg/mm2, but the stress of the specimen after solution heat treatment and water quenching was σt=28kg/mm2 and σz/=60kg/mm2 at maximum.
(2) The residual stress in the center of the specimen was decreased to a half of its original value by ageing at 170°C for 24 hr. after water quenching.View full abstractDownload PDF (866K) -
Makoto TSUKUDA1970 Volume 20 Issue 7 Pages 357-372
Published: July 30, 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (1498K) -
1970 Volume 20 Issue 7 Pages iiia
Published: 1970
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (106K)
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