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Volume 37, Issue 4
Displaying 1-9 of 9 articles from this issue
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Yoji AWANO, Motoyuki NAKAMURA1987 Volume 37 Issue 4 Pages 255-260
Published: April 30, 1987
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSEffects of molten metal treatments particularly melt superheating or melt heating at high temperature above 800°C on the shape of shrinkage cavities in practical ADC 12 alloy castings were studied. Shrinkage cavities in the castings made from secondary alloy ingots change in shape from porous to pipe-like by melt superheating. The pipe-like cavities are often formed in vacuum degassed castings and virgin ingots. Change of shrinkage cavities in ADC 12 alloy castings made from secondary alloy ingots depends both on dissolved gases and some melt properties, but is unsusceptible to metallic impurities.View full abstractDownload PDF (1956K) -
Effect of solidification conditions on microstructure of directionally solidified 356 aluminum alloyShigeharu KAMADO, Makoto TSUKUDA, Ichirou TOKUTOMI, Kikou HIROSE1987 Volume 37 Issue 4 Pages 261-267
Published: April 30, 1987
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSEquiaxed and columnar structures are formed in lower and upper ends and in other parts of unidirectionally solidified castings respectively. This structural difference depends on constitutional supercooling parameters. Fine particles of Si are formed by eutectic reaction at cooling velocities above 1°C/s. Rod-like Si crystallizes at lower cooling velocities. As for T6 treated castings, the tip of Si crystals is rounded, but still remains a rod-like form in the castings solidified at lower cooling velocities. Primary and secondary dendrite arm spacings shorten with increasing these solidification parameters. Correlations of VLC (cooling velocity in liquid state)and DAS1 (primary dendrite arm spacing)and Of VS4C (partial cooling velocity from liquidus to the temperature at which 40% volume fraction of solid solidifies) and DAS2 (secondary dendrite arm spacing) in the columnar structure have the maximum correlation coefficient as: DAS1=305V-0.520LC and DAS2=34.8V-0.350S4C.View full abstractDownload PDF (1437K) -
Shigeharu KAMADO, Makoto TSUKUDA, Ichirou TOKUTOMI, Kikou HIROSE1987 Volume 37 Issue 4 Pages 268-276
Published: April 30, 1987
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSSolidification conditions and mechanical properties of unidirectionally solidified 356 alloy were studied by means of stepwise regression analysis. The elongation of as-cast alloy is strongly affected by average cooling velocity in the solidification range and temperature gradient. 0.2% proof stress is negatively affected by temperature gradient and moving velocity of solid-liquid interface. Partial cooling velocity from liquidus to the temperature at which 40% volume fraction of solid has solidified has a significant effect on ultimate tensile strength, Brinell hardness, maximum load, crack initiation and propagation energy, and total absorbed energy in instrumented impact test. As to T6 treated castings, partial cooling velocity has an effect on tensile and impact properties except maximum load. Maximum load, crack initiation energy and total absorbed energy are strongly affected by moving velocity of solid-liquid interface.View full abstractDownload PDF (989K) -
Tadakazu OHNISHI, Koichi YOSHIMURA1987 Volume 37 Issue 4 Pages 277-284
Published: April 30, 1987
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSFatigue tests in dried air and in aerated 3.5% NaCl aqueous solution were conducted on 7475-T651 specimens extructed in LS, TL and ST directions. Fatigue properties in air are anisotropic and superior in the order of LS, TL and SL directions. Fatigue properties in NaCl are further inferior in failure life, fatigue limit and crack propagation rate to those in air. The specimens tested in NaCl have similar but intensified anisotropy to those tested in air. The anisotropy is attributed to the grain orientation aimed in the manufacturing process and is significant in cracking. The corrosive NaCl atmosphere facilitates initiation and propagation of cracks particularly at low stress amplitude and deteriorates fatigue properties. Deterioration of fatigue properties is attributed to localized hydrogen embrittlement to some extents.View full abstractDownload PDF (2171K) -
Masahiro OKUMIYA, Yoshiki TSUNEKAWA, Itaru NIIMI, Tsutomu OZAKI1987 Volume 37 Issue 4 Pages 285-290
Published: April 30, 1987
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSδ-Al2O3/Al composites were fabricated by high pressure infiltration and extruded at high temperatures. The plastic flow in extruded matrices is classified into two types, namely a laminar flow in the surface region and a turbulent flow in the core. The wider the laminar flow region, the better the fiber alignment obtained. The laminer flow region extends at lower Vf and lower extruding temperatures. Surface defects, fir-tree-type cracks, easily grow at high Vf. The δ-Al2O3/Al alloy has tensile strength twice as much as that the matrix alloy extruded in the same way.View full abstractDownload PDF (1004K) -
Shigeoki SAJI, Shigeru SENDA, Shigenori HORI1987 Volume 37 Issue 4 Pages 291-299
Published: April 30, 1987
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSTensile tests were carried out in the temperature range from 4.2 to 293 K for 5083-O aluminum alloy. Temperature dependences of strength, ductility, toughness, work-hardenability, serrated deformation and cracking within intermetallic particles have been investigated in details especially from 4.2 to 70 K.
Increasing trends of the uniform elongation, the true stress corresponding to the ultimate tensile strength, toughness and the work-hardening exponent with decreasing temperature were changed drastically to decreasing trends below about 20 K. These changes in temperature dependences of the mechanical properties are due to the discontinuous slip of dislocations corresponding to large serrated flows on the load-displacement curves which appear in the temperature range from about 20 to 4.2 K. A large serrated flow was accompanied by a local heat generation. The discontinuous slip of dislocations corresponding to large serrated flow caused decrease in the work-hardening exponent and accelerated cracking within the large intermetallic particles.View full abstractDownload PDF (1839K) -
Yasushi TANIGUCHI, Norio FURUSHIRO, Hideo TAI, Shigenori HORI1987 Volume 37 Issue 4 Pages 300-305
Published: April 30, 1987
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSAge hardening behavior and precipitation structures were investigated for ribbons mainly of both an Al-1.8%Cr-1.7%Zr alloy and the alloy with the further additional element of Si, which were prepared by a rapid solidification method using a single roll. Then, the role of Cr or Si in the precipitation hardening process has been examined.
As a result, age hardening took place more remarkably in the Al-1.8%Cr-1.7%Zr alloy than that in a Al-1.7%Zr binary alloy. It is condidered that this is caused by the precipitation of fine and spherical particles of the metastable Al 3Zr phase with the Ll2 structure, which has been made possible because the additional element of Cr retards the precipitation with the grain boundary reaction. By the addition of Si, together with Cr, to the Al-1.7%Zr alloy, the precipitation of the fine and spherical particles of the metastable phase has been accelerated. Thus, the addition of Si results in reaching higher values of the peak hardness.View full abstractDownload PDF (2173K) -
Teruo MIYASHITA, Koichi YOSHIDA, Hiroshi SANO, Yoshiro TANAKA, Takashi ...1987 Volume 37 Issue 4 Pages 306-312
Published: April 30, 1987
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (976K) -
Takashi KUROYANAGI1987 Volume 37 Issue 4 Pages 313-326
Published: April 30, 1987
Released on J-STAGE: July 23, 2008
JOURNAL FREE ACCESSDownload PDF (1643K)
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