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Volume 50, Issue 12
Displaying 1-8 of 8 articles from this issue
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RESEARCH REPORT
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Gosaku KAWAI, Koichi OGAWA, Hiroshi TOKISUE2000 Volume 50 Issue 12 Pages 643-649
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSIn present study, various aluminum alloys pipe to steels pipe were friction welded, and the mean value and scatter of welded joints were investigated. That is, thirty specimens for each combination of three aluminum alloys pipe to five steels pipe were friction welded under the optimum friction welding condition and the joint efficiency of welded joints were evaluated by tensile test. After performing statistical analysis and Weibull analysis on the joint efficiency, the following results were obtained, (1) The joint efficiency of A6061/steel showed a normal type distribution, but the A5052/steel and A6063/steel showed a distortional type and a double peak type distribution, respectively. (2) A difference was found in the joint efficiency of A5052/carbon steel and A5052/stainless steel showing high joint efficiency in the A5052/S45C and A5052/SUS304. (3) In the A606l/carbon steel and A6061/stainless steel, no difference was found in joint efficiency. (4) In the case of A6063/carbon steel, any difference of the joint efficiency was not found, while a difference was found in the case of A6063/stainless steel. (5) A reference table on the joint efficiency and joint strength for three aluminum alloys pipe to five steels pipe was presented.View full abstractDownload PDF (484K) -
Keiyu NAKAGAWA, Teruto KANADANI, Norio HOSOKAWA, Tadashi TANIMOTO2000 Volume 50 Issue 12 Pages 650-654
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSIn this paper, we investigated effects of aging at 473 K on the relationship between microstructure in the vicinity of the grain boundaries and fatigue strength for Al–1.2%Si alloy. Results obtained show the following features. (1) The fatigue strength lowers with increasing aging time, however, when the aging time is more than 18 ks at 473 K, the fatigue strength remains almost the same. (2) When the aging time is more than 6 ks, grain boundary precipitates with a size greater than several 10's of nm are observed. (3) When the aging time is 18 ks, an accumulation of dislocations are observed at the grain boundaries and in the vicinity of grain boundary precipitates, and dislocations increase with the number of stress cycles. (4) When the aging time is more than 6 ks, the fatigue fracture surface is mainly intergranular. These results suggest that reduction of fatigue strength results from propagation of microcracks which are initiated at the large precipitates on the grain boundaries.View full abstractDownload PDF (632K) -
Yoshinori NISHIDA, Hiroaki ARIMA, Jin-chun KIM, Teiichi ANDO2000 Volume 50 Issue 12 Pages 655-659
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSECAP (Equal-Channel Angular Pressing) can produce large strains in a billet without decreasing its original diameter or thickness and therefore is an attractive process for the production of alloys with fine grained microstructures. However, since the strain per pass through the die is not large in ECAP, about 10 passes are required to obtain a desired fine microstructure. In conventional ECAP, the pressed billet must be removed from the die and reinserted back for the next pressing cycle, making the ECAP process inefficient and difficult to control. The latter problem is eliminated in ECAP with a rotary die. Tests with an AC4C alloy have shown that ECAP processing up to 20 passes is possible without billet removal. After 10 passes, the AC4C alloy showed 2–3 μm grain sizes, which enhanced the tensile ductility at 723 K up to about 126%. The tensile specimens showed a smooth surface after testing.View full abstractDownload PDF (554K) -
Shigenori HORI, Kimio SAITO, Takashi HASEGAWA2000 Volume 50 Issue 12 Pages 660-665
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSLithium possesses a wide spectrum of industrial uses. However, lithium is an immature metal with regard to the field of materials engineering. Accordingly, the tensile test as well as plastic workability measurements were carried out at room temperature. The results obtained are yield stress: 0.4 MPa and elongation to rupture: 28%. Since lithium is a very ductile metal, it can therefore be made thinner by rolling. During the rolling operation, lithium plate “work softening” happened after the work hardening. It is thought that the softening is due to the dynamic recrystallization that comes from the heat energy accumulated by the rolling. The applied stress-time to rupture data for pure lithium determined at room temperature. The grain boundary sliding were observed in the creep ruptured specimens. Next, microvickers hardness measurements were also carried out. At low temperatures the hardness increased with decreasing temperature. The increase was sharper in the lithium and the temperature at which the increase start was about 0.3 T/Tm (Tm: melting temperature). This value is higher than 0.1 T/Tm of iron or bcc refractory metals. Superior deformability of lithium in the liquid nitrogen were confirmed by torsion and bending tests.View full abstractDownload PDF (698K) -
Hayato OKUMURA, Shigeharu KAMADO, Yo KOJIMA2000 Volume 50 Issue 12 Pages 666-670
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSThe Mg2Ni alloy was homogenized by a multi-stage heat treatment to assure the single phase, and its protium absorption and desorption characteristics were investigated. The results show that the Mg2Ni alloy containing a small amount of MgNi2 phase can be obtained by the heat treatment just below the peritectic temperature. The PCT curve shows two plateaus of Mg and Mg2Ni in the as-cast specimen. However, the plateau pressure of Mg solid solution is hard to appear in the heat-treated specimen because it is homogenized during the multi-stage heat treatment. Both activated as-cast and heat-treated specimens absorb protium at room temperature. They have higher protium contents than before activation. This phenomenon is caused by new surface formation and an increase in reaction area due to activation. As the elapsed time after taking specimens out from hydrogen atmosphere increases, the protium desorption temperature decreases and desorbed protium content increases. The decrease in desorption temperature is caused by a decrease in microtwinning in Mg2NiH4 low temperature phase. Also, grinding the powder of the hydride leads to similar improvement of hydrogen desorbing characteristics.View full abstractDownload PDF (512K) -
Yasuyuki KANENO, Shigenari MINAMI, Toru SHIMIZU, Takayuki TAKASUGI2000 Volume 50 Issue 12 Pages 671-675
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSCold rolling and mechanical properties of unidirectionally solidified Al–Al3Ni strip produced by an open type, horizontal, heated mold continuous casting process were investigated. As-cast and heat-treated strips were used as starting materials for cold rolling. Cold rolling was done in two ways in which the rolling direction is parallel and perpendicular to the casting direction, i.e., the longitudinal direction of Al3Ni fiber. Edge cracking during cold rolling was reduced by the heat treatment, and also by cold rolling perpendicular to the fibers. Corresponding to edge cracking, lateral spread of the strip was greater in the case of cold rolling parallel to the fibers than in that perpendicular to the fibers. Heat treatments before cold rolling reduced the tensile strength of rolled sheets, while cold rolling enhanced the strength of cast strips. Although tensile strength of the as-cast strip largely depended on the direction of the fiber alignment, cold rolled strips showed less anisotropic tensile properties.View full abstractDownload PDF (589K) -
Takehiko WATANABE, Atsunori INAGAKI2000 Volume 50 Issue 12 Pages 676-681
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSPlated copper-silver thin layer was employed to braze commercially pure titanium (CPTi), and the tensile strength and the microstructure of the brazements were examined. The following conclusions were drawn from the present study. CPTi could be successfully brazed by using the plated Cu–Ag thin layer as filler metal. The brazement with the plated Cu–Ag had the tensile strength equivalent to the base metal, and the strength could be achieved at lower temperature and in shorter brazing time than the brazement with plated Cu layer or eutectic conventional filler metal consisting of Ag and Cu. The strength of the brazement with the plated Cu–Ag increased with brazing temperature and dwelling time at the brazing temperature. This was ascribed to the disappearance of brittle intermetallic compound phases, such as TiCu and Ti2Cu in the brazed region. The larger the bonding pressure was, the faster the intermetallic compound phase disappeared, resulting in the brazement strength increased at lower temperature and in shorter dwelling time at the brazing temperature. The brazement with plated Cu–Ag filler metal showed sufficient corrosion resistance in corrosive environments of 35°C NaCl solution and nitric acid solution. In addition, the brazement was fairly equivalent in microstructure of the brazed region and the strength to the brazement with the filler metal which was developed for exclusive use to titanium brazing.View full abstractDownload PDF (775K)
REVIEW
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Shigeharu KAMADO, Yo KOJIMA2000 Volume 50 Issue 12 Pages 682-688
Published: 2000
Released on J-STAGE: March 30, 2007
JOURNAL FREE ACCESSDownload PDF (976K)
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