All issues
Volume 23, Issue 2
Displaying 1-6 of 6 articles from this issue
- |<
- <
- 1
- >
- >|
-
Kunio Okimoto, Tomio Sato, Toshio Yamakawa1976 Volume 23 Issue 2 Pages 39-47
Published: March 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThree different testing methods for measuring the tensile strength of metal powder compacts are performed and compared with the conventional uniaxial tension method. These are a test in which a disk is compressed diametrically (disk compression test), a test in which a ring is compressed diametrically (ring compression test), and a bending test. Powders used are reduced iron powders, " electrolyticcopper powders, 'and atomized aluminium powders.
It is shown that a correlation, may exist between uniaxial, tensile strength and, bending, strength, and in anticipation of about ±15 per cent error uniaxial tensile strength is nearly equivalent to the value that is multi-plied bending strength by 1/3. The mechanism of fracture in the disk compression varies with the kind of powder and the green density, so that the disk compression test is not suitable for a testing method to estimate uniaxial tensile strength. In the ring, compression test there is a.question how to take the stress concentration factor, and moreover, the strength varies with. the rate of inner diameter with respect to outer one even if, the green density is all the same. Therefore the ring compression test is not suitable for, it too.View full abstractDownload PDF (3570K) -
Isao Konda, Hidetsugu Yagi, Toshiyuki Nakagawa1976 Volume 23 Issue 2 Pages 48-54
Published: March 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThis study was undertaken to examine the influence of filling pore with copper on the fatigue strength of copper-infiltrated sintered iron compacts by means of microscopical observation of the aspects of its fatigue fracture under low and high cycles.
The following conclusions are obtained from the investigation.
1) The tensile strength of copper-infiltrated sintered iron compacts exhibits the same value irrespective of green porosity by filling pore with copper in the same sintering condition.
2) In copper-infiltrated sintered iron compacts, the inflection point of the S-N curve is not clearly observed, and the curve is similar to that in cast iron, and the fatigue strength for the time rises differently from S-N curve of sintered iron compacts.
3) The fatigue strength of copper-infiltrated sintered iron compacts is not influenced by the green porosity under low cycles.
Under high cycles, the fatigue strength of the test pieces with the green porosity of 15% has the same value, but for the specimens with the green porosity over 15%, it falls as well as the sintered iron compacts, due to the difference in the shape of infiltrated copper.View full abstractDownload PDF (6562K) -
Tadatoshi Honda, Youichi Tokunaga1976 Volume 23 Issue 2 Pages 55-60
Published: March 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSCompletely reversed plane bending fatigue tests were carried out using sintered iron compacts made from five different iron powders. The fatigue specimens with sintered densities in the range of 6.2-7.0g/cm3 were prepared by single compacting and sintering at 1200°C for 1 hr in hydrogen. The fatigue limits of various specimens were measured, and the fatigue microcracks were observed by optical microscopy.
The patterns of fractured surfaces were also investigated in a scanning electron microscope.
Results were summarized as follows;
1) The type of S-N curves for sintered irons showed no difference between iron powders, snd the endurance limits of them increased with increasing sintered densities.
In comparison with the same sintered densities of them, the fatigue strengths of electrolytic and reduced ore iron powder compacts were higher than that of atomized powder. The fatigue ratios were found to be in the range of 0.40-0.47.
2) Fatigue microcracks were initiated at the edge of the specimen, small pores or non-metallic inclusions with porosity of the specimen surface, and then the main fatigue crack for final failure was formed and grew from pore to pore in mixed transgranular-intergranular mode.
3) At the early period of fatigue life, the pattern was partly the grain boundary fracture, and at the final period, it was mainly the ductile dimple pattern by the shearing fracture.View full abstractDownload PDF (5070K) -
Tadatoshi Honda1976 Volume 23 Issue 2 Pages 61-67
Published: March 05, 1976
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe intergranular fracture appeared on the tensile fractured surfaces of vacuum-sintered irons has been studied.
Specimens were prepared from electrolytic, atomized and reduced ore iron powders, followed by single compacting under the pressure of 2-7 t/cm2, and by sintering for 1 hr in the temperature range of 800-1150°C in vacuum (2-4×10-5 mmHg).
Results obtained were summarized as follows:
The intergranular fracture behavior was, particularly, remarkable in higher density of iron powder compacts, sintered at higher temperature of γ-iron region in vacuum, and depended on the strain rate, but not very on the type and the particle size distribution of iron powders.
When the vacuum-sintered irons were reheated for 1 hr at 1150°C in dry hydrogen, the fracture features of them were changed from an intergranular mode, into a transgranular one, these coarsed ferrite grains became again finer, and the tensile properties of them were improved remarkably.
It was suggested that this behavior was caused by the impurities (e.g. oxygen and carbon) in the iron powder and the sintering atmosphere, and by the abnormal ferrite grain growth of the vacuum-sintered irons with passing through Ar3 point of iron.View full abstractDownload PDF (6277K) -
Hikaru Nagai, Sang-hee Cho, Takashi Yamaguchi, Hiroshi Kuno1976 Volume 23 Issue 2 Pages 68-72
Published: March 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSMechanism and kinetics of the solid state reaction have. been studied with special emphasis on the effects of aggregation of reactant powder particles. Equimolar mixtures of BaCO3 and TiO2 were prepared by partial precipitation and ball milling methods using two kinds of TiO2 powders with approximately the same ele-mentary particle size in different states of aggregation.
It is shown that BaTiO3 is the only product when fine TiO2 was used but that aggregated TiO2 yielded additional products Ba2TiO4 and BaTi4O9. Disintegration of large TiO2 aggregates by ball-milling decreased the amounts of additional products, and prolonged ball-milling led to substantially the same reaction products and kinetics as those observed with fine TiO2. No single rate equation has been successfully applied to reaction isotherms obtained with different mixtures. Kinetic behavior has been interpreted in terms of the relative amounts of the reaction products as influenced by the state of aggregation of reactant powder particles.View full abstractDownload PDF (1812K) -
Osamu Yamaguchi, Yoshiki Nakajima, Kiyoshi Takeoka, Kiyoshi Shimizu1976 Volume 23 Issue 2 Pages 73-75
Published: March 05, 1976
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSIt was found that enstatite (MgO⋅SiO2) was directly formed at low temperatures, without passing through forsterite (2MgO⋅SiO2), by heating mixed powders prepared by the simultaneous hydrolysis of magnesium and silicon alkoxides.View full abstractDownload PDF (656K)
- |<
- <
- 1
- >
- >|