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Volume 41, Issue 2
Displaying 1-11 of 11 articles from this issue
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Mitsugu MOTOMURA, Tsunehisa SEKIGUCHI1991 Volume 41 Issue 2 Pages 77-83
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSFrom the view point of reducing the weight of automobile and their energy consumption, the use of Al-Si alloy forging parts is attracting attention to the automobile industry. The microstructures affected to the mechanical properties of Al-Si alloy casting small bar in the order of elongation, ultimate-strength and yield strength. Mechanical properties and forgiability were improved remarkably when DAS became under 20μm. The cutting properties were improved except for chip treatment when microstructure was controlled fine and homogenious. In order to obtain good mechanical properties, it is necessary to control microstructures as same as chemical compositions of alloy.View full abstractDownload PDF (1356K) -
Genjiro MOTOYASU, Atsumi OHNO1991 Volume 41 Issue 2 Pages 84-88
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSAl-1 mass%Cu alloy specimens were cast by the heated mold continuous casting (Ohno Continuous Casting) method developed by the authors. The specimens were cold worked by torsion. The relationships between the twisting workability, crack initiation, mechanical properties and structures of the specimens were examined and compared with those of the specimens produced by chill casting and hot working method. When the angle of torsion was increased, the chill cast specimens tended to exhibit crack initiation in the solidification grain boundary and fractured easily, but the OCC and the hot worked specimens were twisted smoothly and were free from such defects. The twisting fatigue life of the OCC specimens was 1.8 times that of the hot worked specimens and three times that of chill casting specimens. Mechanical properties of the twisted OCC specimens, such as hardness and fatigue strength, were superior to those of the twisted chill cast and the twisted hot worked specimens.View full abstractDownload PDF (1512K) -
Toshiro KOBAYASHI, Hiroyoshi IWANARI, Heon-Joo KIM, Eui-Pak YOON, Shui ...1991 Volume 41 Issue 2 Pages 89-94
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSMetal matrix composite fractures in a complicated manner such as exfoliation between matrix and reinforcement or failure of reinforcements. Therefore, evaluation of fracture toughness becomes important for the application as structural materials especially from the view point of the guarantee of higher security. In this study, the effect of volume fraction of SiC particles on the fracture toughness and fracture mechanism of 6061 aluminum alloys reinforced with SiC particles (SiCp/6061-T6 composites) manufactured by powder metallurgy process were investigated by characterizing with fractography and microstructure. It was found that dynamic fracture toughness and crack propagation toughness were remarkably decreased with increasing the content of SiC particle. Furthermore, volume fraction of SiC particles in SiCp/6061-T6 composites showed a great influence on the crack propagation toughness. The micromechanism of the fracture process in the lower volume fraction of SiC particle was concluded as follows: 1, voids were formed at the ends of SiC particles, 2. voids grew and coalescenced, and then crack propagated. Stable voids growth was difficult with increasing SiC particles. Eventually the rapid unstable fracture occurred.View full abstractDownload PDF (913K) -
Kiyoshi SEKIGAWA, Mamoru KOBIYAMA1991 Volume 41 Issue 2 Pages 95-101
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSPotentiostatic polarization measurements were carried out for the three single crystal planes, (100), (110) and (111) planes, of 99.99% aluminum in pH 1.0 hydrochloric acid aqueous solutions with and without the four aliphatic carboxylic acids (RCOOH; R=H, CH2=CH, Me and Et). The acids make ico decrease in the order CH2=CHCOOH>HCOOH>MeCOOH>EtCOOH and the order is about that of the acid strength. The decrease effect on the single crystal planes is in the order (110)>(100)>(111) planes. The observation on the crystal planes by an optical microscope shows that the corrosion pits occur at Epit in the HCl solution and the addition of the four acids makes area and depth of the corrosion pits decrease. The strength of the acids (except HCOOH) for the above three acids corresponds to the decrease of ico.View full abstractDownload PDF (1430K) -
Shinji TERUTA, Kazuhiro FUKADA, Masafumi MIZOUCHI1991 Volume 41 Issue 2 Pages 102-107
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESS3004 base aluminum alloys cold-rolled to sheets are known to show age-hardening in the case of Cu, Mg and Si existing in solid solution. The solid solution state is usually obtained by rapid quenching from relatively high temperatures such as by CAL annealing method. In this work, the behavior of precipitation and solid solution of copper during intermediate annealing was investigated for the 3004 alloys containing 0.14 to 0.45%Cu. Copper was found to be retained in solid solution even in the case of slow cooling of 50°C/h from annealing temperatures above 370°C. This resulted in age-hardening in the cold-rolled sheets aged at 160°C for 2 hours. The present heat-treatment condition was easily obtained by conventional box type annealing.View full abstractDownload PDF (1106K) -
Mamoru MABUCHI, Tsunemichi IMAI, Katsushi KUBO1991 Volume 41 Issue 2 Pages 108-113
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESS6061 aluminum alloy matrix composite reinforced with silicon nitride whisker was fabricated by hot press and hot extrusion, and superplastic behavior of the composite was investigated by tensile test at elevated temperature (818K). The maximal elongation of composite was about 250% and the m-value was about 0.4 with an initial strain rate 1.6×10-1s-1, while the maximal elongation of 6061 alloy fabricated without whisker under the same condition was 190% with an initial strain rate 1.6×10-3s-1. The grains of composite were very fine (3μm). The high ductility of composite might be attributable to suppression of void formation due to less amount of slip at the interface between matrix and whisker.View full abstractDownload PDF (1863K) -
Yoshinari OKI, Ryoji TSUNO, Masashi NAKAMURA, Yoshihiro YOSHIDA1991 Volume 41 Issue 2 Pages 114-118
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSIn the present work, a die which is named hemispherical core die, has been developed for hollow extruded shapes of 6063 aluminum alloy. The endface of the core of the die is hemispherical on entry side of a billet. The maximum tensile stress appearing around the root of a mandrel of the core is remarkably reduced in comparison with a porthole die, which results in suppresion of crack initiation. The hemispherical core die is designed and manufactured, based on calculation of stress distribution by FEM. FEM analysis showed that the core weight and the maximum tensile stress around the mandrel of the new type of die are respectively lowered to 12% and 26% those of the previous type of die. A hemispherical core, manufactured on the base of the FEM analysis is lightened to 13% and the extrusion pressure is lowered to 96% of the previous type of die.View full abstractDownload PDF (478K) -
Masahiro YANAGAWA, Shojiro OIE1991 Volume 41 Issue 2 Pages 119-125
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSInfluence of Mg content, grain size, 0.2% proof stress, and alloying elements (such as Zn, Mn, Cu, Y) on the ductility of Al-Mg alloys have been investigated, and controlling factors have been revealed. The uniform elongation is expressed by εu=n(1-σo/σi) where n is the strain hardening exponent, σi the true ultimate tensile strength, σo the 0.2% proof stress, and εu the uniform elongation. The strain hardening exponent n increases as the Mg content increases, which depends on the increasing difficulties of the cross slip of dislocations. The 0.2% proof stress σo decreases as the grain size increases, which increases the uniform elongation εu.View full abstractDownload PDF (986K) -
Hiroji YAMAGUCHI, Mitsuyuki ISOGAI, Satoshi MURAKAMI1991 Volume 41 Issue 2 Pages 126-135
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (1804K) -
Hiroshi SHIMA1991 Volume 41 Issue 2 Pages 136-143
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (1963K) -
Hiroshi URAKAMI1991 Volume 41 Issue 2 Pages 144-145
Published: February 28, 1991
Released on J-STAGE: October 30, 2008
JOURNAL FREE ACCESSDownload PDF (229K)
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