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Volume 22, Issue 11
Displaying 1-7 of 7 articles from this issue
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Basic studies on solidification of welds (5th report)Toshiyasu FUKUI, Keizo NAMBA1972 Volume 22 Issue 11 Pages 651-660
Published: November 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThis paper discusses morphology of feather structures observed in aluminum alloy welds and effects of these structures on some properties of welds.
The feather structures are observed locally at reinforcement in the center of weld heads and seem to be nucleated after columnar structures have been developed. The characteristic features of the feather structures have very little difference from those formed in cast common aluminum alloys. Formation of the feather structures is remarkably influenced by welding speed. As welding speed decreases, the feather structures become less populated and co-exist with granular structures. From these observations it is considered that formation of the feather structures is also influenced by constitutional supercooling besides various factors mentioned previously. The feather structures are also closely related to grain size and width of granular structure regions. The number of the feather structures decreases remarkably by refining grains and increasing granular structure regions. Consequently, formation of the feather structure is possibly prevented by refinement of weld-solidified metal.
Formation of the feather structure results in deterioration of mechanical properties, saw-tooth like marks in fracture, and change of a propagation mode in weld cracking.View full abstractDownload PDF (2455K) -
Hisashi SUZUKI, Motohiro KANNO, Shigenori ASAMI1972 Volume 22 Issue 11 Pages 661-667
Published: November 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSThe role of Cu in aging phenomena in Al-Zn-Mg-Cu alloys was investigated by hardness and specific heat measurements and transmission electron microscopy. Various specimens, based on (α+T) type Al-Zn-Mg alloys, with a nearly fixed amount of 5.5at% in (Zn+Mg) and with different Cu contents were used. The specimens were solution-treated at 470°C for 2hrs, quenched into iced-water, and finally subjected to aging at various tempera tures. The results obtained were as follows:
(1) As Cu content increased, the initial rate of age hardening and the maximum hardness attained at 125-150°C aging increased. The time required for hardness to reach the maximum also increased. This indicates that the quarternary alloys are superior to the ternary alloys with respect to hardness and heat resistant characteristics.
(2) Specific heat measurement and observation on transmission electron microscopy showed that two sorts of precipitation processes would exist in Al-Zn-Mg-Cu alloys when Cu contents exceeded about 0.7wt%. One process was that observed in Al-Zn-Mg alloys and the other was that observed in Al-Cu-Mg alloys.
(3) Clusters or precipitates, which were formed in the present quarternary alloys and corresponded to those in Al-Cu-Mg alloys, were considered to be responsible for the peculiar aging phenomena in the quarternary alloys.View full abstractDownload PDF (1141K) -
Michio KIKUCHI, Shotaro MOROZUMI1972 Volume 22 Issue 11 Pages 668-672
Published: November 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSCast magnesium billets, in which various amounts of extruded magnesium powder (EP) phases had been embedded along the longitudinal direction, were extruded. The composite extrusions were tensile tested at temperatures from 20°C to 300°C. The results obtained are as follows:
(1) High proof stress of EP was partly due to the effect of the Orowan interaction between dislocations and dispersed oxide particles and was largely due to the fine-grained structure caused by the dispersed particles.
(2) Over testing temperatures, proof stress of the composite extrusions with up to about 10% of EP was higher than that of the non-composite extrusions (Specimen 0), while ductility of the former was almost equal to that of the latter. However, ultimate tensile stress of the extrusions was not improved by composite forming. The composite extrusions with more than 10% of EP were inferior to Specimen 0 with respect to tensile properties.
(3) EP was quite brittle over testing temperatures. However, the composite extrusions with up to 10% of EP was fairly ductile.
(4) Clear discontinuity, corresponding to fracture of EP, on stress-elongation curves of the composite extrusions was observed at 20°C. At higher temperatures, however, this discontinuity was not observed.View full abstractDownload PDF (632K) -
Toshihiko KAWASHIMA, Takao SHIBATA1972 Volume 22 Issue 11 Pages 673-677
Published: November 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSEffect of pre-aging on 150°C aging characteristic of an Al-4.58wt% Zn-1.63wt% Mg alloy was investigated by means of resistivity measurement, tensile tests, and transmission electron microscopy. Two-step aging, first, pre-aging at 120°C for 6 hours and then, aging at 150°C, resulted in an increase of proof stress. In this case, over-aging occurred at the same aging time with or without pre-aging at 120°C. When an aging treatment, suitable for formation of G. P. zones, was performed prior to the above two-step aging, the distribution of precipitates became finer, higher proof stress was obtained, and over-aging was accelerated. Resistivity changes were also affected considerably by the pre-aging treatment to produce G. P. zones.View full abstractDownload PDF (769K) -
Tsuneo TAKAHASHI, Takeshi MURAKAMI1972 Volume 22 Issue 11 Pages 678-683
Published: November 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSRolling and recrystallization textures of aluminum single crystals with the initial orientation near (100)[001] were studied with an X-ray pole figure method and a metallographic method. The results obtained are as follows:
(1) In crystals rolled about 50%, slip rotation took place around the transverse direction and a uniform cell structure was observed on a transmission electron microscope. However, with about 80% reduction, a rolling texture with two components symmetrical to the transverse direction was formed and a large number of prominent slip bands were seen parallel to the rolling direction.
(2) Beyond 90% reduction, a rolling texture, which was described nearly as a {358} <523> texture and had two components symmetrical to the transverse direction, was produced.
(3) It was found that the cube texture, developed on annealing, had an orientation relationship with both components of the rolling texture. The orientation relation was described as rotation by 4044° around the common <111> axis.View full abstractDownload PDF (1067K) -
Takakado NAKAYAMA1972 Volume 22 Issue 11 Pages 684-693
Published: November 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (1259K) -
Takuichi MORINAGA1972 Volume 22 Issue 11 Pages i-ii
Published: November 30, 1972
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (204K)
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