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Volume 45, Issue 4
Displaying 1-10 of 10 articles from this issue
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Teruo OHASHI, Hiroshi YUKAWA1995 Volume 45 Issue 4 Pages 175-180
Published: April 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSP/M Al-Li alloys containing a large amount of Mn were made by using a rapid solidification technique to prevent the formation of coarsened Al6Mn phase. The changes in mechanical properties and microstructures of these alloys with aging time were examined. The solute Mn does not depress the precipitation hardening ability of Li, but increases linearly the hardness and tensile strength, especially Young's modulus, of the as-extruded or as-quenched alloys with its amount. Most of the solute Mn is dispersed in the matrix as the Al6Mn particles the size of which is in an order of submicron. Heat treatment usually employed for the Al-Li alloy adds the precipitation hardening by Li to the hardening (dispersion type) by Mn mentioned above. Increases in the density of the Al-Li-Mn alloys with increase in Mn content can be compensated for by Li.View full abstractDownload PDF (1955K) -
Wataru FUJITANI, Yukichi UMAKOSHI1995 Volume 45 Issue 4 Pages 181-186
Published: April 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSPlastic behaviour of α-phase binary Mg alloys containing Al, In, Li, Sn or Zr was investigated at temperatures between 77 and 573K. Addition of In, Sn, Al and Zr increased yield stress of these binary alloys, while Mg-4%Li alloy was softened by Li addition at room temperature. Mg-4%Al and Mg-4%Li alloys showed good ductility but no significant improvement in ductility was observed in other alloys. Activation of deformation twins which was observed by characterizing the acoustic emission signals during tensile test was responsible for good ductility of Mg-4%Al alloy, while addition of Li activated the non-basal slip resulting in improving ductility of Mg-4%Li alloy at room temperature.View full abstractDownload PDF (1408K) -
Hiroshi ONO, Seiichiro TOMITA, Hiroshi ISHII, Akihiko OGASAWARA1995 Volume 45 Issue 4 Pages 187-192
Published: April 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSAluminum suspension parts are usually formed by die forging process. This process shows high level of dies and material costs, because of the utilization of aluminum extrusion and forming in three sets of dies. Therefore the portion of the forging process is replaced with casting one to save the cost. This process, named 'cast/forging process', uses one set of dies and the workpiece made by casting. But reduction of the forging process decreases plastic deformation in the product. And it also decreases the mechanical properties. Therefore the effect of the forging process on the mechanical properties is investigated. The distribution of equivalent plastic strain in typical forging products is calculated by FEM. As a result, the forging die configuration and the workpiece shape suitable for the 'cast/forging process' are presented. One of suspension parts is also formed as an experiment. The static fracture strength in the trial parts is measured. Results obtained satisfy the requirements.View full abstractDownload PDF (1183K) -
Hidetoshi UCHIDA, Hideo YOSHIDA1995 Volume 45 Issue 4 Pages 193-197
Published: April 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSn value of Al-Mg alloys is not constant with strain, since it increases to a maximum and decreases. The changes of n value and microstructures during tensile deformation suggest as follows. When n value increases with strain, dislocation density increases. When n value is stable with strain, microstructures change little. When n value decreases with strain, the formation and growth of dislocation cell structures occur and cause to dynamic recovery. The stability of n value is more important than the maximum n value to obtain good formability. The alloys having stable n value with wider strain region are considered as materials with better formability.View full abstractDownload PDF (1124K) -
Shinji KUMAI, Jianqun HU, Yakichi HIGO, Shigetomo NUNOMURA1995 Volume 45 Issue 4 Pages 198-203
Published: April 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe fatigue crack growth behavior of a Al-Si-Mg base cast aluminum alloy (AC4CH) has been investigated with special reference to the effects of solidification structure. Fatigue crack growth tests under the constant load amplitude condition have been perfbrmed using CT type specimens of systematically controlled solidification structures with such as dendrite arm spacing, size and morphology of eutectic Si particles and matrix aging conditions. The results were discussed from view points of microstructures and fracture mechanics. The da/dN-ΔK relationship reveals that refining and spherodizing of eutectic Si particles improve fatigue crack growth resistance in the high ΔK range, while the crack growth rate at the lower limit range is not influenced by morphology of the particles. Matrix aging condition influences little the near-threshold and the Paris regime fatigue crack growth. The crack growth resistance in the high ΔK range is improved by increase in ductility of matrix. It is, however, deteriorated by the coarser dendritic structure which yields the higher crack growth resistance near the threshold level.View full abstractDownload PDF (2313K) -
Shinji KUMAI, Akinori SEKIKAWA, Jianqun HU, Yakichi HIGO, Shigetomo NU ...1995 Volume 45 Issue 4 Pages 204-208
Published: April 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSThe role of extrinsic mechanism which improves fatigue crack resistance of the cast alloy has been examined. A constant load amplitude fatigue crack growth test and a crack closure measurement have been performed using AC4CH cast aluminum alloys. The da/dN-ΔK relation and the crack closure levels were compared between the cast alloys and squeeze cast or powder-metallurgy processed 6061 aluminum alloys. Improved fatigue crack growth resistance at the low ΔK range was shown for the cast alloy in comparison with the powder-metallurgy alloy with finer microstructure, when evaluated by the da/dN-ΔK relation. While, the difference was diminished by evaluaion based on the da/dN-ΔKeff relation. This indicates that the roughness-induced crack closure effect is large in the cast alloys to improve the crack growth resistance in the low ΔK region. This extrinsic mechanism is considered to be originated from the deflected fatigue crack growth path and the resultant rough fatigue fracture surface, which are attributed to the dendritic solidification structure and the eutectic Si particle distribution in the cast alloy.View full abstractDownload PDF (760K) -
Masahiro INOUE, Katsuaki SUGANUMA1995 Volume 45 Issue 4 Pages 209-213
Published: April 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDense and thick Ni aluminide plates are successfully fabricated by the in-situ reaction by using squeeze casting of pure Al into pre-sintered Ni forms in the low temperature range in air. The compositions of Ni aluminides can be controlled by changing the porosity of initial Ni forms. Two different Ni aluminides layers 50-100μm thick, which are Al rich, are formed between Al and the Ni aluminides. Microstructures of Ni aluminides are quite fine in the range of less than one μm to a few μm.View full abstractDownload PDF (1980K) -
Minobu SUKIMOTO, Tatsuo OTSUKA, Mitsuharu MATSUZAKI, Hitoshi AKIYOSHI1995 Volume 45 Issue 4 Pages 214-225
Published: April 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (2043K) -
Akira TAJIRI1995 Volume 45 Issue 4 Pages 226-246
Published: April 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (2957K) -
Tetsuichi MOTEGI1995 Volume 45 Issue 4 Pages 247-248
Published: April 30, 1995
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (255K)
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