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Volume 18, Issue 8
Displaying 1-4 of 4 articles from this issue
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Tadatoshi Honda, Youichi Tokunaga1972 Volume 18 Issue 8 Pages 295-301
Published: April 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSYielding behaviors of sintered iron compacts were investigated through the microscopic observations and the tensile tests at both room and high temperatures with different strain rates.
Yield drop, named as pseudo yield point, in a stress-strain curve is observed in various iron compacts, pressed at 3-7 t/cm2 and sintered in hydrogen for 1 hr at 1200°C. This behavior, which differs from that of mild steel as to the existence of plastic strain before yield point, may be due to the yielding of matrix and subsequently to the stress relaxation by nucleation and propagation of the crack from residual pores. The pseudo yield point and tensile strength of sintered compacts may depend en the strain rate (10-5-10-2/sec) as in the case of mild steel.
The strength increment due to strain aging and the serrated stress-strain curves known as blue brittleness are clearly observed in iron compacts sintered even in hydrogen. Furthermore, this phenomenon is remarkable in the high nitrogen iron compacts sintered in dissociated ammonia.View full abstractDownload PDF (2035K) -
Isao Konda, Kumao Okita1972 Volume 18 Issue 8 Pages 302-306
Published: April 25, 1972
Released on J-STAGE: May 22, 2009
JOURNAL FREE ACCESSAlthough many investigations have been made on the mechanical properties of sintered iron compacts, few have been made on the fatigue behaviour. The fatigue strength of sintered iron compacts is one of the most important factors when it is used under repeated stress. Since the sintered iron compacts generally have many pores; the purpose of the present work are as follows; to investigate the notch effect caused by the stress concentration arising from pores at the tensile and fatigue tests, and then, to further investigate the relation between the tensile and fatigue strength.
The following conclusions are obtained from the above investigations:
1) As the porosity of sintered iron compacts is increased, the tensile and fatigue strength are reduced. But when the porosity is constant, the pore size and its shape have influence on the tensile and the fatigue r strength-particulary, stronger influence on the latter than the former.
2) Most of sintered iron compacts have the fatigue ratio (the ratio of the endurance limit to the tensile strength) in the range of 0.23-0.6, and the fatigue ratio decreases with increasing porosity.View full abstractDownload PDF (2984K) -
Takashi Daikoku, Masaru Ikenaga1972 Volume 18 Issue 8 Pages 307-315
Published: April 25, 1972
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn this investigation, the authors tried to improve the elevated temperature properties, in particular, creep rupture strength of the fully ferritic steel by employing the technique of dispersion strengthening. As a result, it was found that the sintered alloy steels with dispersed fine T-A12O3 particle, especially those obtained by the technique of the liquid phase sintering and the hot-working after sintering, have higher creep rupture strength than those of the wrougth steels having nearly the same compositions, and that these dispersion strengthened steels are promising as a new type of heat resisting material.View full abstractDownload PDF (9206K) -
Shinichiro Omori, Yasuhiko Hashimoto, Keiichirô Shôji, Ken ...1972 Volume 18 Issue 8 Pages 316-320
Published: April 25, 1972
Released on J-STAGE: December 04, 2009
JOURNAL FREE ACCESSIn order to determine the liquidus surfaces, the ternary system Ni-B(<30 at %)-Si(<30 at %) was studied by thermal analysis, X-ray diffraction and the observation of microstructures. The results obtained are summarized as follows:
(1) The phases appeared in this region were Ni(solid solution), Ni3B, Ni2B, Ni3Si, Ni5Si2 and Ni6Si2B.
(2) Quasi-binary eutectic reactions took place at the boundaries of liquidus surfaces of Ni(solid solution) and Ni3B; Ni3B and Ni2B; Ni(solid solution) and Ni3Si; Ni3Si and Ni3B; Ni3B and Ni6Si2B; and Ni2B and Ni6Si2B. Monovariant-peritectie reactions took place at the boundaries of liquidus surfaces of Ni5Si2 and Ni3Si, and Ni5Si2 and Ni6Si2B.
(3) Following four invariant reactions with melt were observed at the intersections of the above i monovariant reaction lines;
L(11 at %B, 13 at %Si)+Ni5Si2=Ni6Si2B+Ni3Si at 1012°C
L(12.3 at %B, 12.0 at %Si)+Ni6Si2B = Ni3B+Ni3Si at 1002°C
L(9.8 at %B, 12.9 at %Si)=(Ni)+Ni3B+Ni3Si at 993°C
L(20.3 at %B, 9.8 at %Si)=Ni3B+Ni2B+Ni6Si2B at 991°C
Thus, the liquidus surfaces have been experimentally determined.View full abstractDownload PDF (2411K)
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